Here comes the high-mileage myth again! Never ever let mileage put you off a vehicle, especially with a Land Rover because in many cases, it is totally irrelevant. In a lot of cases the mileage is usually only a record of the distance the the chassis its self has covered, and that is if the owner hasn't fiddled with the dial or driven around with it disconnected like I did for the first four months of ownership! The engine may well have had extensive work (in the way of reconditioning) or it may well have been replaced. Then again, if the previous owner has looked after it and serviced it once or twice a year, that engine could be in the same shape as some that have only covered 150,000 miles. It's very likely to have had most of the usual parts replaced such as wheel bearings, half shafts, prop shaft UJ's, swivel housings and the like but I'd strongly suggest that you have a look through the service history and ask to browse any receipts that he has. That way, you'll know exactly what work has been done to the vehicle, when it was done and therefore when it's likely to need doing again. As mentioned earlier, if you're happy with the vehicle and you don't mind paying the price, then by all means go for it and try not to have any regrets. There's no harm in trying to bring the price down a little bit however
Just remember to thoroughly check the chassis and remember that they rot towards the back end first. The bulkhead is also important, so give it a good look over, especially down the inside pillars of the front doors (i.e. with door open). Also look down the top edge of the bulkhead where it meets the windscreen at the corners. If it's rusty here, it'll be rotting away on the inside and it will turn into a very costly job.
You could even get a rough idea as to the condition of the engine too. Let it run up to usual operating temperature and then remove the oil filler cap. Does it bellow oily mist out towards you? If there's a little 'blowing' (blow-by) it's perfectly normal, but if there's a great gush, it's a sign of engine wear in some shape or form. Also, with the engine running, remove the expansion tank / coolant header tank cap and look for bubbles. If there are no bubbles, you know that you haven't got a head gasket leak between a cylinder and a water channel.
Other than that, good luck and post up some pictures!
-Pos