Declan you've certainly not done your customer or yourself any favours. Fitting a genuine cat was the only option, now it's come back and bit you in the arse. I hope for your sake you had the insight to put a disclaimer on his invoice, if not then it's down to you to put it right, you are going to be out of pocket.

I guess you can now say you have built up your experience along the way with what to fit and what not to fit.