He should have replied something like:
Hi Richard,
I'm am very sorry to hear of your displeasure with our recent services. We pride ourselves on our reputation that has taken 36 years to achieve. I'd like to think that we treat every complaint with the utmost respect and will apply any actions that we see fit.
However, it seems that we have had a slight miscommunication upon what was to happen to the part you provided us with. It was our every intention to use it to fit your item, but even after careful manipulation it could not be achieved. I was not aware that we could not try to alter it from its original state, but also we never had any explicit instructions from you to the contrary either.
As a valued customer I hope you understand our situation and agree that it was neither of our faults. We take all complaints seriously and want every client to leave having had a positive experience of our services. In todays current climate, word of mouth, can make or break a business so we would like to offer a contribution of +/- £50 and would hope that that would be satifactory for both parties and enable you to feel confident not only to return to us but also to recommend us to any friend or forum associates you may have any dealings with.
Cheers
Dick Wad Audio Services Ltd
Not blaming your issue on todays compensation culture and basically telling you not to pursue this route as its not a good example to be setting as a Teacher..........