My Uncle has two 2.5Td's. One was getting a bit tired, but had 230,000 miles on the clock. The other was only on 170,000 or so and runs great. Not speedy, but should be more than happy on the road keeping up with modern traffic.
My brother had one a few years back. Well he still has the Land Rover, but it's a Tdi now. That's because I drowned the TD in a big mud hole. It however ran really well up until that point.
A 200Tdi is the easiest swap, but be warned, it's not quite as simple as unbolting a couple of things and doing them up again. There are things you need to do. And with an engine out, you'll always find other things to replace. Expect a fair amount of grunt work and several hundred quid or more, excluding the purchase of the engine.