well, would you believe it, I was entirely wrong.
Took it to bower lane tyres and was under the car with them.
The CAT is buggered, so bad in fact I can put my finger in it from the side, rusty to bits and rattling in and out, everything from there to the back is fine, a little rusty but not too bad.
I could do with a new entire system but it can wait, and gives me time to save the cash for a decent one, so for the time being they will de cat it, put a pipe in place, will give it a slightly better sound but wont rattle, £60+Vat so happy with that.
Then summer next year can get a new system for it.
It does however now need new disks and pads all round, so more expense.