Opinions please - choice of 3 1990s cars

The Jag is an X300 - they are reliable cars. The X300 is basically a face lifted Jaguar XJ40 and has a six cylinder engine which is known for exceptional durability. The Transmission is the ZF4HP24 - a very long lasting and robust unit.

It is the V8 (X308) which has problems with mechanical fragility. The timing chain tensioners on the early V8 have a design flaw and need to be replaced with later metal type, the water pump is plastic and also needs to be upgraded to the later metal type and the transmission is the somewhat fragile ZF5HP. None of these problems affect the X300 and all of them are rectifiable (albeit not cheaply) on the X308. Sadly, it has often not been done though, with predictable results.

The X300 does like to rust though - and the rust on this one concerns me, since they can often be worse underneath than they appear on top. The rear wheel arches are not a cheap fix. I would advise you to check underneath the car in the following areas: the fronts of the floor pans, especially round the jacking points; all along the sill pinch weld - on the floor pan side, not the outside; in the inner wheel arch behind the front shock absorber; the sill ends, especially on the inner side where it protrudes from the body (sill end rust is often present on cars with rusty front wings).

I imagine the Mercedes will be similar to the Jaguar - in that it is a robust and reliable car which is old now and somewhat rust prone. I like the W126, but can't comment on them since I don't know enough about them. They have an imperious feel but lack the road ability of the Jaguar.

The Audi isn't my kind of car and (to me) feels outclassed by the Mercedes and Jaguar - but that is purely personal taste, I'm sure many others would prefer them.