Ok - I wasn't happy with the Piper 4" slashcut tailpipe, it was too short and didn't look right in the bumper cutout. So rather than change the whole exhaust again, I contacted a nearby firm called 'Stainless Creations' who make just about anything, but mainly custom exhausts. I found them by looking around Yell.com. They are based in Falkirk, a 20 minute drive from me.
http://www.stainless-creations.co.uk/
I went out this morning, they agreed that the tailpipe was too short, so they brought out some tailpipes and we agreed on a large oval which fitted the cutout perfectly. They offered to do the job right there and then, so I agreed and they've done a first-class job.
http://i112.photobucket.com/albums/n191/robd67/oval1.jpg
http://i112.photobucket.com/albums/n191/robd67/oval2.jpg
They tacked it on and asked me to check it looked ok before welding it up - end result is the look and sound are both perfect, it's a little quieter inside the car now, probably due to being slightly longer and differently shaped, but for me it's perfect.
Very friendly and helpful guys, good to deal with, happy to recommend them to anyone. I'm going back next month to have them make up some one-off intercooler pipes for my setup, to get rid of most of the silicone bends.