Get a disco 3 mate. Ive had a really nice defender tdi and a discovery tdi prior to mine. A disco 3 is one of the best used car buys at the moment.
I got a great deal through a online car supermarket.
The disco 3 is years ahead in terms of technology, I went for an auto but the manuals drive really well. You can get a D3 s manual with less than 50k for less than 11.5k no probs.
Not sure about the air suspension? Get a 5 seat version they have coil springs!