I have a stainless 'Staintune' muffler fitted to my XT. The baffle is also stainless. They don't do header pipes for the XT though.
They are made here in Australia, so i'm not sure how you would get one over to the UK... Perhaps drop them an e-mail and ask if they have any retailers in the UK??
Even if they don't have any retailers in the UK, your bike shop should be able to call them up and place an order with them.
They are VERY good quality pipes.
Here's their website:
Staintune Exhausts
Dan.
EDIT: Just found a dealer in the UK.....
Sportouring Bike Accessories