Are you looking for a full system from header to tail pipe or just a cat-back system?
I have a cat-back system from
www.longlife.co.uk for £250, mid-sport note, idles very quietly, burbles beautifully, and roars fantastically at 3,500 RPM at full throttle.
I am considering getting them to make me up a header and fit a sport-cat as well but the header is £450 and the cat is £250.
They also offerered me a de-cat as well for offroad use, that would be easy to just swap in.
(I don't know whether those are reasonable prices. I just really struggled to find anywhere that did what I want.)