Exhausts...

We took our omega in yesterday for exhaust inspection and quote- took the car back this morning to get the middle boxes replaced. Three hours later I was told the one cat converter needed replacing and the flange got damaged when they removed the pipes (they have welded a piece of metal to "fix" the problem). The garage claims its not their problem as the exhaust was old and they struggled to remove the pipes. The exhaust is now blowing and rattling really badly with a damaged cat!
Does anyone know where I stand with this??
I cant afford £200 to replace a cat at the moment and dont feel I should as it was working fine before they started messing around!
Any advice/suggestions will be greatly appreciated.
Thanks
Greg

No thats not in writing.
When I was there I told them they need to replace the cat and the one bloke told me its not their problem!
The car sounds worse than when it arrived and once I left there I took it straight to a friend of mine who is a MOT tester. He says due to the damage the car will fail its MOT now.......

Receipt just lists the parts and the total price.........

Funny thing was when I mentioned where I had the work done at my friends MOT centre his staff all rolled their eyes and none were suprised by what happened!

Thanks for that Toni and kris1anne..............will get the letter sent 1st thing tomorrow!