Right just a few things to let you know about trouble wize with:
land rover discovery TD5
Very good cars, especially if you like mod cons like air con, cruise control, heated leather ect. The face lifted ones look far better then the earlier ones that pretty much look like a 300tdi. Normally have Active Corning Enhancement which is noticeable when throwing about, but only really noticable on the very very limit. Few things to watch out for:
Active Corning Enhancement pipes, they corrode and finally burst under pressure. Pipes are cheep enough but definatly a job I would do without a ramp
Air Suspension, Prone to splitting rear air bags, if the bag has a leak it can lead to the compressor burning out. Easy fix as there is a range of coil spring conversion kits off the shelf but it will cost you a trip to a land rover dealer / specialist to have the compressor turned off via the ecu using their diagnostic computer.
Diff lock, Early td5's did not come with a manual diff lock and traction was reliant on the traction control system, land rover realised their mistake and changed it back to manual locking when they released the face lifted td5's. If you do get an early one it is possible to fit the manual locking selection shafts as it is the same box.
There the main problems with them, I could go on but other stuff is what you find on an abused example.
Land rover defender 90
All depends on what engine, td5's are amazing. colleague at work had one kicking just over 200bhp and it was like a train. just check:
Chassis, get underneath and have a good look, outriggers and rear cross members are all prone to melting away, always a way to knock the price down and their is galvanized chassis out there. If a seller is claiming its a galvo chassis make sure they have the paper work to back it up otherwise it will be a case of them having your pants down
Other then that they are bomb proof and with regular service and maintenance will last for many many years.
Hope this helps mate
Matt