Car appreciation... the aesthetics, the engineering, etc

Jaguar main dealers are going to be pricey. If you buy a car with a FSH from main dealers you're probably going to want to keep it up, but independents are going to be a lot cheaper.

If you go XJ6 the AJ6 straight six is a very reliable engine if properly maintained and not difficult to work on. If you go XJ8 the AJ-V8 is also reliable (it's still in production). You will read stuff about nikasil engine linings in pre-2000 models being eroded by high sulphur fuel between the start of 2000 and summer 2000 when the sulphur content in UK fuel was reduced, but in reality this is pretty much ancient history and any problems would have revealed themselves by now! It should be easy to check anyway as there's a plaque on replacement engines.

The 'sealed for life' ZF gearbox which is not actually sealed for life is also worth knowing about, and a much more pressing problem IMO. There are cheaper ways to get it serviced here but the definitive way is to take it back to ZF in Dortmund for a service:
http://www.bimmerboard.com/forums/posts/527361

(That article is well worth anyone reading just for the engineering/photos!)

But all in they are (broadly) well built, reliable cars that did well in J.D. Power surveys.

Bear in mind I've never actually owned my own car, I'm just a bit obsessed with 90s Jags :)