save up about 1500 quid, get your self a fully reconditioned unit from power enginering or another reputible company, switch to efi (for reliability although not 100% necessary) get it all in and running about 200 bhp (this seems to be a reliable figure.)
and enjoy the car.

with 1500 you could proberbly get a 2.0 zetec with lower compression (this can bedone by machining the head) and running your existing management and turbo.

if your loom foocked get a replacement at £100 max.

the best thing about the rs is its so simple, im still at school, never been to a mechanics coarse or anything, and ive changed rs engines and done nearly every engine job on one apart from rebuilding the bottom end and ive done this with knowlage ive picked up over the years and a hynes manual.

give up on your current shite engine and get a new one in !!!!!!!!!!!!