B&B has both 1 5/8" OD and 1 3/4" OD w/ heat that bolts on. Or since you are in the UK Hayward &Scott may be able to help you.
A word of warning, the B&B headers are fine but do have a proprietary spacing for the muffler inlets. I wouldn't use the b&B mufflers too many headaches there. Fab up a Flo-master or equivalent.
something like this
