A couple of reclusive people have died near me leaving apparently no will and no known relatives.

If this is proven to be the case, then after a couple of years the case is referred to the Bona Vacentia Department , part of HM Treasury. They will then publish details on their website allowing Genealogy firms to try and trace heirs - heir hunters. Eventually the state will claim all the assets if no heirs are found.

I wondered what happens if there is a property involved, does it just sit there unused and unloved?

Well it turns out that our good friends in the local authority are responsible for safeguarding and maintaining(!) the property even to the extent of insuring it - all paid from our funds. But the properties remain unused /unoccupied, and that to me seems completely wrong when there is under supply of housing.
Current Eon Next customer, ex EDF, Zog and Symbio. Don't think dual fuel saves money and don't like smart meters. Chronologically Gifted. If I offend let me know by private message, but I’ll continue to express my opinions nonetheless.