not even a day after i posted the first post in this thread, was driving along the M53 when the exhaust fell off...
got the AA out, and they find that the reason the exhaust was blowing was because of the bolt that attaches the catalytic converter to the chassis (gearbox i think, correct me if im wrong) was missing, causing it to crack, so after 2 exhaust repairs under warranty when i got it last year, and two different garage visits in the last week, noone thought to check it! going to buy the cat tomoz,and keep the car off the road till the whole system has been finished.