I had a P38 for about yrs. Now own a Disco.
Air suspension is not the only issue on the P38; a good `un is a lovely drive but good`uns are hard to find now. Many have been bought by people who think, because they`re getting cheaper, thy`re gonna be cheap to run... they`re not. Many are being sold within your budget, but repairs can be very expensive. P38s are diy-able but many (not all) will require lots of effort (and time and cash) to keep in good nick.
Personally I chose a 300tdi Disco to avoid all possible problems with electrical suspension & engine management systems. OK, less comfort than a TD5 but for me it`s a price I`m prepared to pay.
Try to test drive a couple of examples of whatever you`re interested in. Maybe you`ll fal in love with the P38, and take a chance on one, maybe you`ll prefer the comfort of a TD5, or maybe opt for the more basic, character of the earlier Disco?
Anyway good luck, and take your time choosing.