I would think you can get it for Free. Or near enough.
Buy a complete 200tdi Disco that runs, but is a MOT failure rot box.
Maybe between £500-£600 depending your luck.
Take your engine & sell the rest as best you can on Ebay & For sales & weigh in the rest.
You are selling the Turbo, gearbox, transfer box etc, so depends how good they are.
Or if you buy a good engine from someone else doing that same thing, expect it rto be from arounf £200-£500 just to get the engine.
Its a seems to be a sellers market just now for good engines.
Maybe the person doing your conversion has a better chance of getting you an engine.
george