Well, my exhaust has been clattering against the underside very loudly when going over bumps for the last few days, had a look yesterday and it seems that the hooky hanger metal bits that are welded onto the side of the back box have come off. Because my car is French, the welds failed before the rubber bits that suspend the exhaust did. I'm not paying out for a new exhaust when the rest of the actual exhaust is still in very good nick, so these metal bits where the weld's failed are now held onto the back box by means of 5 jubilee clips attached end-to-end going round the whole back box. Before the fix, seems like the whole exhaust was being held up by just one rubber hook half way along the car. Hopefully I won't be seeing sparks coming from the back half way up the M1 now...