I've been to see the car today. Thankfully it's still in one piece. The visible damage to the bodywork, as far as I can tell, is (relatively) minor. The steering column and ignition has obviously been damaged, and from the look of the rear tyres it seems that they've had some fun with the car : I'm pretty certain that burnouts / doughnuts or drifting have been the order of the day. Having seen the state of the car, and with the limited information I have about its movements after it was stolen, I would say almost certainly that it was taken by so-called 'joyriders' rather than someone with any particular knowledge of the car who wanted it for parts or to sell it.
Fortunately they abandoned the car after getting a flat tyre, otherwise who knows what might have happened to it (I shouldn't think they have thought twice about turning it into a burnt out shell if they'd managed to get it to a quiet area). Obviously it will need a very good inspection of much of its internal workings to check what damage has been caused to the clutch, engine, gearbox, suspension etc., but it was still great to see the car.
I hope this will put some minds at rest about there being a 300zx specialist preying on the cars. Initially I thought this was the case, but the instant I saw the car (especially the tyres :eek: ) I changed my mind about the motive.
Thanks once again for all the posts: I appreciate the warm welcome (under not-ideal circumstances). Any advice on possible damage to look out for as a result of the car being ragged by joyriders would be warmly received.