With regards to the earlier point about the MOT situation on a Category D - as far as I'm aware the MOT remains valid on a Cat D, but is automatically withdrawn on a Cat C. Would be interested for someone to clarify if there's a bit more to it than that though.
It would make sense though, as the MOT is only evidence of roadworthiness when the test was carried out so it seems daft to invalidate it automatically, especially when Cat D can apply to all sorts of situations which couldn't feasibly affect the MOT - paintstripper attacks etc. The car is obviously unroadworthy at the moment, but being roadworthy and holding a current test are two different things.
It would make sense though, as the MOT is only evidence of roadworthiness when the test was carried out so it seems daft to invalidate it automatically, especially when Cat D can apply to all sorts of situations which couldn't feasibly affect the MOT - paintstripper attacks etc. The car is obviously unroadworthy at the moment, but being roadworthy and holding a current test are two different things.