Mini One Catalytic Conveter Issue

Hi all,

I bought a 07 plate mini one about 2.5 months ago. It had a MOT just before I bought it and everything was fine..

A month ago I had a crash where some 18 year old boy on his phone smashed into the back of me pretty hard. He accepted liability straight away. It went to a garage for repairs which took 3.5 weeks. I had it back a few days and the catalytic converter light has come on.

I took it back to garage who stated "they wear and tear, nothing to do with the accident" and I have to pay for it to be fixed. There was no problem with it before the crash and the MOT was only done 3 months ago. Am I right to contest this? Anyone know anything about these catalytic converters.

Any help is greatly appreciated

Thanks