Hi, Thank you. You do not need to send it registered mail. Just post it to him first class. If he does not read it and continues to chase you tell him over the phone it is harassment and just report the matter to trading standards.
If he is ignoring your correspondence then he is clearly not prepared to be reasonable about this and is simply trying to bully you to pay.
I presume he has not actually issued any court proceedings against you? Kind regards AJ
no, I did not get anything from him. I was just worried that he might do it on purpose - to say afterwards that he thought I agreed to pay. i shall resend the letter 1 class. Thank you. Kind regards, AK