jecasc - 8:54 pm on Sep 9, 2011 (gmt 0)

I'd send a payment reminder - not by email but by normal mail, set a fixed date until the payment should be payed and tell the customer that I would pass on the collection of the debt to a debt collection agency if the debt is not payed and also get the police involved.

If the payment would not arrive I would search a debt collection agency in the UK online and then let them try to collect the payment. Some of them work for commission, so if they do not collect you do not pay.