id go for the Megane conversion from Hill Power mate
main reason bein, you get a new engine with that, well, one with 30k on or less, but you also get a Lumenition ECU, which usually on its own costs £400
it isnt a big jump in power, but its still workable the engine, and you got more time to do it, and it wont be wasted on an engine thats gonna die in a year or two
plus as long as your insurance company dont mind engine conversions it will still be cheaper than a 16v etc, which i know is probably one of the main reasons your considerin a transplant