2000 rpm the limit ?

Hi I have a 2000 Freelander with the 2.0 diesel engine, just recently when the car warms up after say 10 miles of constant running the car slows down losing its rpm and even with the foot to the boards will only reach a maximum of 2000 rpm. When cold the car runs perfectly, I have heard of this type of fault before but Ive trawled the forum and cant find anything to try and explain what it might be !, can anybody please advise ?

Sounds like the low pressure fuel pump is on it's way out. This lives behind the rear drivers side wheel arch. Mine did exactly the same as you describe. If you can, go for a genuine part as the aftermarket one I have is very noisy.

If I'm right you've got the Rover L-Series power plant...I remember that the low pressure fuel pump is a niggle of the Td4 BMW engine, and on the cars with the Rover engine there is no pump behind the rear driver's side wheel arch.
I think you have to search for your problem's solution in your engine bay, perhaps something related to the EGR valve that could be very dirty "suffocating" the engine.