Im in cardiff too, member of south wales land rover club as well. couple of us have v8's
My knowledge of them could be written on the dry bit of a disco carpet, but its a learning curve mate! anyway, if you do have a 3.5, or 3.9 with a 14cux ecu then gimme a shout, Ive got a ecu reader that will help when its running or not as the case maybe!!
Only reason I mentioned the club is there is some peeps there that are local to us and have the tools,facilities to give you a hand. mate. me included.
Good luck with the engine search.