As JJ says....remap and a decent suspension set-up....
Either on your existing car or on a replacement (manual) CDi....personally I'd favour the latter.
As to which set-up.....
? Hmmmmm.....
KW is THE benchmark....but why not try the BC version (series BR) that is made for the Colt that
B8TFKhas fitted on his. Though he did say he had to 'modify' the rears...maybe he can explain that mod ?
The only problem on either of these is the price.....the BC's can be got for around £650....the KW's for £1000 !
Not cheap by any means...but you only get what you pay for......and you do get a lot for your money with these.
Longer life, better ride, adjustable ride height and rebound.....
and a car that will handle unbelievably afterwards.