http://www.legislation.gov.uk/uksi/1.../contents/made
I only skim read it but from I understood the law relates to modifying the exhaust so it could be argued that if the baffle was fixed it stays put. If it is removable then would removing it be a modification or would it simply be using it one way that was intended? I think it's ambiguous enough you could argue but the axe may fall either way.
Also I think there is a Euro law restricting machines over 175cc to 82Db..... not sure if that applies here if it does it would override the above.
