My advice - Don't buy the first one you go to look at - there are lots out there,
If you have never brought one before then get hold some of the folks on here to go with you when you do find one you want to buy so they can all pass their critical eye over it (I did this even at the main dealers!),
Don't be frightened to buy from a main dealer - they have the newest and best stock, but they won't stock cars older then 6 years old/100,000 miles and they do charge the highest prices.
If you can afford a used Puma 2.4TDci (even though they have lots lecky control units that don't like water) the engine in them is fantastic.
There is no such thing as a cheap Defender....................... if you find one that is cheap to buy then it is going to cost you a lot to put it right!
In 2002 I spent ?10k on buying mine - I set out with a budget of ?1000.............................. and saw lots of rubbish that was only fit for spare parts. I still have it, although in the nearly ten years in between it has continually had money spent on it - converted from a hard top to a stationwagon, new tyres, new galvanised chassis after the original started to turn to dust, new suspension, hydraulic winch fitted...................... it also runs faultlessly which is very important for a non-technical person like me and it gets a full check up and service every year even though these days it's lucky to drive more than 3000 miles in that time, but it is heavily offroaded when it gets used and has given me many many hours of fun.