Closed Road hillclimb in the UK,... Where would you do it?

Ooo Tough one.
locally the Strines would be perfect. or up Holme moss (again the A635)

Box hill is actually a good shout as it provides somewhere for spectators to go and the course could be interesting with those switch backs and there is enough road around there that people could live with the closed roads.

Going to check out the A635 as well...

Cat & Fiddle looks like an EXCELLENT road... Could definitely do a nice closed road event there, there are even lanes going off it you could route traffic through!

Box Hill is actually National Trust private road for most of it...... has cafe and pub at the bottom and a number of car parks... and car parks and stuff at the top. Hmmmm what are the chances of the National Trust wanting some screaming hillclimb cars heading through their area of outstanding natural beauty?

Might need a couple of temporary chicanes on the straighter bits. _{(The A502 route obvs. Not the tube...)}

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Hmm, not sure if the locals would be keen though.

End of the seafront up beachyhead

Box Hill would be quite good as they have closed it for cycle races etc so the local council would know a bit about how to do it.
Looking at the route they used for the Olympic Cycling might give a few ideas.

My first thought was Zig Zag road, Boxhill. Not sure how possable it is now as I'm sure its covered in speedhumps, probably due to it being used as an unofficial 'event' location in the past. As Zoompod says there are loads of roads in the area that would be perfect for it, the area is full of hills and twisty roads. There is already Shere hillclimb that takes place which isnt far from boxhill.

South Harting near Goodwood / Uppark House.

It was actually used in the early days of motorsport.

From the oracle that is wikipedia...

In the 1920s Harting Hill (now the B2141 road) was the venue for one of the most important motor hill climbs in the country, with Frazer Nash, Aston Martin and Raymond Mays (Bugatti) participating.

Though it may need some barriers to make it safe for todays nuns and kittends brigade, there is a 'slight' drop.  Possibly could tie it in with your 'discussions' with Goodwood and has a useful car park at the top..
map

I 'may' go out of my way sometimes just to 'enjoy the view' when its quiet...

As for Boxhill, i think its more the local residents who are already slightly miffed due to the number of bike races that may be the issue...

Loads of possible places around the Surrey Hills. In fact, it happens there already, the Shere Hill Climb up at Staple Lane.
I must admit, when I read about the new ruling, I thought "what's changed?" Having been to the Shere and kop hill climbs, which have been on closed public roads for years,
Good luck with Box Hill! It's a cycling Mecca....