Living without a modern car, anyone do it?

Depends on your definition of modern really and your level of mechanical ability. Certainly anything from the 60s onwards should be able to be daily used unless you do a lot of motorway work

I think it's do-able as long as you keep on top of all the little niggles so they don't grow into bigger issues.

I ran a Triumph Stag as my daily drive for about 5 years.

My Dad has a 2000 Corolla which is the 'modern' car although he hardly puts any mileage on it.
He uses his Lotus VI for car shows, fine weather runs, attending track days, etc.
The car they tend to use most is their Gilbern Genie, the Ford V6 lump is pretty reliable & it still goes like the clappers. As a nod to his advancing age, (78), he put power steering in it last year as the steering was pretty agricultural, (I don't know if it's the only Genie around with p.a.s.? He had a hell of a job fitting it but the Invaders seem to take p.a.s. with far less modification being required). With a car like this there is always something 'starting' to go so you need to catch it before it actually goes. In the last couple of years he's had to replace the back axle, major suspension components, gearbox seal, (gearbox out job), the electronic ignition he installed about a decade ago started playing up so he put the points back in, etc. he had a fully body restoration a decade ago and this year it's going back in for another full body resto, (which will be £6-7K). He's replaced the Britax sunroof, had some of the seats re-upholstered.
It's a balancing act, they get immense enjoyment from using the Gilbern but it does demand regular attention & ££'s (as did my Stag). They could go out & buy a new-ish car & not worry about maintenance but they're not going to enjoy it as a car plus it would depreciate.
What they spend annually keeping the Gilbern in good order probably just exceeds what they'd lose in depreciation if they went out & bought, for example, a nearly new Honda.
The Saab is an excellent car, I had one years ago, but it's also a good example of a manufacturer whose products depreciate at a rate of knots.

A new or newish car which is going to be hassle free motoring for a good few years but depreciate in value.
or,
An interesting classic which will constantly require attention, maintenance & repairs but won't depreciate in value, (and will likely increase in value).

I know which option I'd plump for, (with AA cover!)

This is the difference between occasional / fine weather use & everyday.
If you everydayed your 1300, then 5 years from now you're not going to be getting away with £120.00 pa running costs!
I seem to recall that when the Austin Allegro was released the marketing boast was that it had been designed to comfortably accommodate 4 x 6"+ Welsh Guardsmen.

I use my 79 volvo 240 every day. It's fine after some upgrading of service items (it's done 170k)
My weekly usage is a 30 mile return journey to work every day, supplemented by a 50 mile motorway journey once a week. No bother, although the ride is firm due to lows.

However, my wife has a 54-reg V50 which we use for longer journeys because it can sit at 70+ all day while doing 50mpg, air con, it's quieter and it's comfier.

Never owned anything newer than 12 years old, daily for the last 5 years has been an 89 ford, wifes "new" car is a 97 escort and my modern disability car is a 99 pug 106 old or new some need constant looking after some don't, appart from once a year oil changes (i rebuilt the cooling and start/charge system when i got the car) i havn't touched the car in 5 years BUT it will catch up with me/you, daily use will take it's toll and there will be bigger bills, costs may be lower than a modern but finding parts can take time, you can have it quick OR cheap not both, you either save time OR money never both unless you carry a shedload of spares "just in case".

Dez and MkX have got it pretty well covered.
It really does depend on your definition of "modern" and then more than anything else on your planned uses and your mechanical skills plus having the space/place to do maintenance/repair.

Fuel consumption, unless you do astronomical mileages, is a red-herring. Depreciation on a modern car will wipe out fuel savings without even trying. Compounded even more so if you're paying for the thing on HP etc.

"Modern" cars may apparently give the illusion of better reliability until you are the poor sap who has got one of the "take me to the workshop and leave your wallet" specials. The FBHVC are already holding talks/seminars as to what to do about the increasing number of "modern" vehicles for which parts are becoming rare due to many parts being unique/specialised/CAD-CAM'ed to specific models and said parts no longer being obtainable.

On the other hand if you go back too far for your non-modern motoring you could also end up in much the same position because most of the cars of your chosen type have been scrapped so survivors and parts can be expensive. If your chosen model is even reasonably rare it also becomes desirably stealable. You can also add in that if you go back too far you may be seriously compromising on crash safety too.

You have to strike a balance that suits you: Do your research, find out which models have odd-ball parts that cost a fortune to replace (just for some examples (before we start a spat, there are plenty of others), this month's Car Mechanics: lovely Toyota MR2 Mk3 : dealer price for a power-steering motor fitted: £1597.50. Second-hand £50-£100 provided you can fit it. 1996 Nissan Almeira self-contained distributor/coil-pack dead: new unit £495 + vat, no delivery time given and once ordered will not be accepted for return if diagnosis wrong. Dealer has none in stock, will only be ordered when and if, sufficient wanted for a large enough order. Vehicle is now SORNED!). Bad news if you haven't got somewhere to put it for SORN.

Continuing on the "research" line find out which vehicles are within your personal servicing/repair capabilities, or for which you can budget a certain amount of cash for garage time. If you've got the space lay in a complete spare vehicle so you have access to things like glass, door panels, interior trim that always seems to go extinct just when you need it. Stick to the same type of vehicle so your worn out one can yield bits for your next one (esp true of headlights etc).

Then put your classic car enthusiast hat back on and forget all the rules when your "special" comes along :-)
That's why I've got a 5.3 litre Jaguar Sovereign V12 and 15 mpg. Of course my 41 years worth of research on the type told me many of its parts come from the Leyland/BMC parts bin so should be readily available (that's my justification and I'm sticking to it). I even found that Falken do a lovely modern tyre for it that outperforms the originals and costs only about a quarter of the price too. Of course your choice could go the other way: there are some Jaguars out there that take a special size in metric tyres and if you want to stay original then you are going to pay big pounds for those tyres. Like I said do your research.

At the moment she is actually my daily driver in all but name having covered some 7,000 miles in the last year (very reliably too (touch wood)). My two other non-moderns are currently undergoing a typical enthusiast on-going refurb limited by cash and my time. One, a 1990 G reg Renault Espace Quadra is nearly done to MOT status and will become the daily hack as we have house refurb work on the go too. The other a 1984 Renault Trafic Rapido Caravanette of 1647 cc is a longer term project.

Not that many years ago there were plenty of both these vehicles available in AutoTrader and on Ebay, but since then the Scrappage scheme and time has decimated them. Luckily I have scrapped off a previous model of each and saved all the good/useful spares even including engine/gearboxes and drive shafts ready as future spares for these two. Even so with my attempt at future-proofing I missed out: I'd love to add 4WD to the caravanette (as per the Trafic 4x4 that Renault used to make), esp useful on grassy camping sites, but the 4x4 version (even a scrapper from which I could rescue the necessary parts) has virtually become extinct in the U.K. You see the odd one on European web sites at extortionate prices!

It ain't an easy decision, in the end you have to reason it out for your way of life, and if just occasionally the heart doesn't over-rule the head, then the whole exercise would be very boring anyway.

The newest car I've ever had is the little 5 I have at the moment, it's a 1994 but they were designed and made in 1985 so somewhat old - makes for a fun daily driver. It copes with everything nicely except speedbumps, and I use it more like a van than a car.

Before that I was using my Escort as a daily driver for work in the winter until the salt came down and that's 40 years old, I couldn't imagine driving a modern car tbh

You're exactly the type of person I tend to buy cars from. Spend a fortune doing all the expensive stuff, conclude the car is now expensive to maintain, so sell up. I've bought many a car like this, run them for a year or two without any major expense, just general servicing and TLC, then sold for pretty much what I paid.

Well if you're tired of it, I guess that's as good a reason as any! It'll make a cracking buy for someone going on the bits you have mentioned replacing.