Any number of the usual suspects will do an engine change for you - GEMM, Strathearn Engineering, Lix Toll etc. You'd have to have the conversation about who supplies the engine, warranty ( if any) etc. Steve Parker - already mentioned - do bits, as do MD Engineering. Get googling...
The general advice seems to be that a 200Tdi will blow a series gearbox & transmission to bits relatively quickly BTW, so plan on maybe fitting it as a 200Di - no turbo ?
Whats the main thing you are after - faster, more economy ?