Paul you have built up an excellent reputation, all by word of mouth/internet etc, & being one of your 1st customers i will always phone you. The sad thing is no matter how good of a reputation you have, people will always listen to the bad things
Meet him half way, refund him £20 or something. Its WRONG you should have to, but just call it a lesson learnt.
BTW, when you send parts out, to you mark them in anyway so you no there yours, just incase he did send the fooked ones back?
& if its anyone off here...NAME & SHAME them