fodder I know the dealer you are talking about, I know the people that you are talking about, I just brought a new Duc from them, they have MOT'd my last 2 Ducs for me. I was talking with them last week trying to encourage them to post here on this message board asgain as they did a while back. That dealer will not take a bike in p/ex unless it has road legal exhausts.
My understanding is that the loop hole is that they and other MOT stations do not have decibel meter to be able to test the sound, however if an inspector was to pick them up for passing a blind eye to a sign that read "not for road use" there is a chance that that MOT station would loose its license. This year all licensing duties pass to Borough and City Councils, if you know as i do the Borough Council that would license this dealer, - well look for any excuse springs to mind. IMO it just aint worth the risk of putting on a public forum the names of MOT stations that turn a blind eye, - as they themselves are bike riders.
It is my opinion that the days of us riding loud bikes are numbered, - old bikes no problem, - but my new Duc has a sticker on its frame listing decibel readings, now that is there for a reason, - MOT time in 3 years that sticker will have to match the exhaust.