To be fair, they were polite & backed off after I'd explained the situation, well before I thought of pointing them to his work location!

Heh, let the flat upstairs in our house as s/c unit. One guy unknown to me paid zero CT and moved out after 6 months. Next I knew, bailiffs were round threatening to take MY stuff for HIS debt. Put them in pic and they were v. polite, immediately backed off. On the plus side I was able to tell them where he worked (he'd left no forwarding addy of course) so they were able to locate him there and arrange for the debt to be taken out of his wage-packet directly, by installments!

I unwittingly hit on the answer to stop these at the first call - I am on the TP 'no cold calls list', but when I picked the phone up had problems hearing them and asked them to explain what they were on about. Having an income of less than £10K a year (I've been medically retired for many years) I had little idea what they meant by PPI and said so, I asked what it was, explained that I'd never had any such thing, and that they must have the wrong person (all their spiel suggested that they were a company who I'd actually had some connection with). The caller soon got bored and put the phone down, had a couple more which went to voicemail and after that I never heard from them again!