I used to work in a shop that serviced quite a few Jags. From a RAM-D* perspective, they are doubleplus ungood. I had occasion to drive a few, and I was utterly unimpressed, but the ones I drove were all newer models. If you like the car and are okay with the possibility that you may spend more time working on it than driving it, then go for it.

RAM-D=Reliability, Availability, Maintainability, and Durability. I used to test vehicles for these characteristics when I was in the automotive testing business.

Edit: James May picked one like that up cheap on one of the Top Gear challenges. When it was running, it was capable of 140 mph. Operative words being "when it was running".

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.