Try http://www.powerflow.uk.com for a local dealer as they make custom exhausts for your car and have a large range of centre exit exhausts.
Black '95 Cinquecento Sporting: K&N, Eon2's, Abarth style spoiler with brake light, Sony MD Head unit, Sony 6x9s, Kenwood 10cm & a stupidly loud 12" Pioneer Sub where spare wheel should be ;-)