Croeso yn ol Stephen!

Don't know whether a chat with these guys might help?:

BMS ESVA

Looks like they'd be able to sort most the details for you? I agree with NIbiker in that insurance might be a pain, you'll be able to get it sorted tho. As far as I'm aware there aren't currently any emmissions checks on bikes, tho they can be strict on pipes, depends where you go. If they're marked off road use only, they'll probably fail. If no markings it's down to the examiner's opinion as to whether they think they're unreasonably loud...
Hope you and family will enjoy your new home near The Dales. Not far from us.. some great roads.. we should catch up sometime.

Sometimes it takes a whole tank full of fuel before you think straight