This has probably been discussed before but these "Heir Hunter" adverts do appear both online and in newspapers. I know these firms take a hefty percentage when they find relatives but surely that's better than it all reverting to the state.
I once had a message on GR from a lady who was a member and had a tree, so presumably a family historian - but was not a relative. She was actually enquiring on behalf of her solicitor employers who were trying to find relatives of my Betsy Whitehead who died as widow Gibson in London in 2010 aged 101, childless and intestate, but with a substantial estate of over £1 million (probably mostly the value of her house, in 1939 she was a waitress married to a cook).
They had identified both of her deceased siblings who died unmarried and childless, and asked if I knew about any more distant relatives. In fact I knew something about four of her many cousins, some of them had parents married back in to closer relatives (again!) and another had a descendant who was a contact.
I was able to put that contact in touch with them, though I never found out what happened. (There were 14 first cousins, all deceased of course, most of the next generation were also deceased, so the final split would not have been a life-changing amount). I was able to tell the employee that two of the cousins were married but childless (not just from records but nearer relatives had known them).