Scenario 1) Mid 1990s, largish close-to-London suburban town (like Orpington, or Reading), and a married couple with a child own a nice detached house. They're professionals. Child is (suposed to be) off at boarding school, the couple are suddenly not seen at their place, nor do they show up for their work (they own a business). Neighbours checking on them might remember them leaving with suitcases, but no-one said goodbye or organised for mail to be stopped or the plants to be watered.
A week later the house burns down in suspicious circumstances.
No bodies are found, yet there's no record of them having left the country and they never return. Enquiries as to the child's school show no record of any such place. Child is 17, seems to have also disappeared but reappears with story of having run away from home, can prove they were far away at the time of the fire.
Would the parents be declared dead, and when? Would the courts have to wait the full 7 years, or would the suspicious circumstances (yet no actual bodies) lead the coroner to declare them dead earlier?
Scenario 2) Present day. Someone who had dropped off the system for various reasons has returned - or have they? They were declared dead many years ago, but came back, got things sorted, got married. Now there's a strong suspicion that the person who is claiming the name isn't who they say they are. The marriage might have been to cover up a case of illegal immigration. Would the couple be interviewed at home? By a Border Force officer? (Is that what you call them?) Or brought into a police station, or taken to a special facility?
1) Faking death (uk), declared dead (uk), the John Stonehouse story, Lord Lucan, John Darwin, no evidence of bodies, no proof of crime.
2) Marriage in the UK, Border Force (watched a lot of episodes :-)), false identity UK, proof of identity.