How to find a guy's paper trail in England.

An aquaintance of mine died alone in London recently. He was discovered by the smell coming from his apartment. He was about 50. He was brought back here by a charity and buried by his parents (in their eighties).

He was not poor. He owned his apartment, and had a car, money and probably business interests of some sort. But despite access to his apartment, we can't find

• His car keys (I'm sure he had transport).
• His laptop or computer (he would have had one)
• His bank account(s) or his bank(s).
• He probably had some business going - wedding photography, window cleaning, something like that. We have no details.
• His solicitor, if he had one
• His accountant.
• At this time we don't even have his insurance number or income tax number.

Now, as the police were involved, they may have taken certain items in an attempt to trace his next of kin. The police failed to trace anyone. My son discovered by chance because the police contacted his local religious congregation, which he had left. They knew someone here in Ireland, and asked him, and two dozen phone calls later, things were happening. Things work that way in Ireland.

My son is going over at the request of the elderly parents to try and do something, but how do you go about tracking someone like that? We will have my son's feet on the ground in a week or two. Is there anything that can be done online? What can he do when he gets there?