Will it pass its mot tomorrow?

No idea what the code was my friends husband is a wizz and he said it stated cat wearing, but last july my front end of the exhaust dropped off and when I took it to the garage for repairs they said they had done the cat, I then a few weeks ago took it bk to the garage and asked what he had done but he was really rude so I walked away, my friends hubby said it may have come on as I dont travel very far and the day it happened I had done a long journey it has been fine for weeks and now this week has come back on, will this affect the emmisions then I assume? And are they expensive to replace? Dont fancy paying the labour but can have it done if I buy the part and ny car is a 206 not 205 as I said by mistake, thank you for emailing me :)