Fil, for exhaust fabrication it would be worth trying Predator in Hatfield-they will make anything. They need the bike to make sure things fit but they are good fabricators.
Predator Motorsport
84 Tewin Road,
Welwyn Garden City,
Hertfordshire, AL7 1BD
United Kingdom
Phone:+44(0) 1707 334050 or 334090
Fax: +44(0) 1707 339009
http://www.predatorexhausts.com/index.html John