I bought a 10 year old honda jazz, and had it MOT'd less than 2 months ago. Without any major pothole bumps I can think of, the front end of the exhaust system became detached was dragging along the road, on a motorway. It would seem to me to have been a pretty terrible MOT! Am I right? And would it be just a simple issue of screwing it back on (ie which I could do, or which would not cost much to fix)..

I agree, provided there wasn't any damage to the exhaust.