So, I found out what was wrong with my exhaust....
I've brought a new one direct from Cobra, but if anyone wants my old one. I'll sell it for FREE + P&P. I can try to arrange delivery or meet half way if your around Brighton or Birmingham or possibly somewhere in between. FYI: a new one from Cobra can be brought for £345 (with a bit of haggling)
I presume it can be fixed by welding the tail pipe back on? If not, it may make a very nice bread bin/garden feature.
It was on the car when I brought it so I can't confirm how it old it is, other than at least 4 years.