You need to draw a distinction between the original version (Rover designed) and the new version that was re-engineered under Ford's ownership.
The original one has either the 1.8K Series or the 2.5KV6, both Rover engines. The 1.8 does have head gasket problems in the Freelander, and I wouldn't recommend it. The 2.5 is a much better engine, but probably thirsty in the Freelander. It only really has one weakness, it's clever inlet manifold. If that goes, it's £550 for a new one. Land Rover designed some uprated parts to fix the head gasket issues on the 4 cylinder engine, which might work.
The diesel versions of the original Freelander are either the Rover L-Series diesel engine on early models (reliable but not common rail so rough and probably a bit underpowered). Later versions came with the BMW 2.0 turbo-diesel engine which was also fitted to the Rover 75/MG ZT. A cracking engine, very similar to the engine in the E46 BMW 3 series.
The newer version of the car "Freelander 2" might only look like a facelift but was a substantially improved car I think. The interior is a hell of a lot better. There is a 3.2 V6 petrol engine and 2.2 diesel petrol engine. They look like the same units that are fitted to the older shape Mondeo ST. Should both be good engines.
If you can afford the newer shape I'd definitely aim for that. I don't think a 54 plate would the Freelander 2 though. 55 plate might be.