I recently had the dilema of which exhaust system to go for on my petrol/LPG 2.6, and I went with longlife stainless steel. At £389-00 inc vat and fitting I think it represents good value as I am quiet lazy and couldn't be troubled to do the work myself. It won't need doing again and it looks a picture. I chose a tailpipe that fits the bumper cutout and it looks as though it was designed for it. The guys built the system on site whilst I waited and it only took about 2 and a half hours. I have crawled about underneath and had a good look at it and it is quite a work of art, and all shiny like chrome. An excellent job with no clamp joints now, just pipes to boxes and all welded, so no specific weak points at joints to collect moisture. I was quoted about £350 for a pattern (mostly Timax) system fitetd and with VAT so it was a no-brainer for me. I would recommend the stainless option. I used the Topgear website and the 'Longlife' system. Very happy with it, and it sounds quiet a bit better than stock - you can choose what sound it makes, quiet, sporty etc. mine is mild sport, but is inaudible at motorway speeds. Has a nice deep burble at idle as well. I used the Basingstoke fitters and they were very good.
Hope that helps.
Paul