If the area he moved from is a small community, eg a village, it might be worth ringing the local post office, if there is one.
The chap might have had his mail redirected when he moved, and the postmaster/mistress might know of him, or have a record of the redirection.
I don't know that they would be allowed/willing to reveal the new address to you, but they might be willing to forward a letter on to him.
It also might be worth ringing the local pubs - someone might know of him.
You could also consider putting an advert in the local newspaper, asking if anyone knows of his whereabouts. That's bound to create some interest....especially from distant relatives who think they might be in for a bit of a windfall. :o)