Alternatively, Hayward & Scott in Basildon are superb. Have a look at the website.
http://www.haywardandscott.com/
Some of their stuff is a work of art.
I had a back box from them for my Impreza, and they made up a custom 3" job for my Saab 9000 Aero and did an amazing job. Have always been tempted to take my S8 down there and see what they can do.
Regards,
Mark