Fascinating thread. I'm from the Wirral, so I know Liverpool well. My own parents had a strange experience, which might be explained by a timeslip?
It was the mid 60s and my mum (to be) was in her late teens, living with her parents and two brothers in a terrace house in Tranmere, the Coronation Street red brick type where the front doors open straight onto the street.
Anyway, my dad (to be) was working and lodging a few streets away, having moved down from Newcastle upon Tyne. He and my mum had become friendly , and had arranged a date. My dad was to call at mum's house that evening to take her out, which he duly did. He knocked at the door, but no one replied. He knocked and knocked, as loudly as he could, but still no answer, so he gave up and went back home to his digs.
The next time they managed to meet up, my dad asked where she had been that evening as clearly noone had been at home. Equally puzzled, my mum replied that she and her parents had all been in that evening, and yet nobody had knocked the door. Remember, these are small two up, two down houses, where you would hear the front door being knocked wherever you were in the house.
I wonder if maybe my dad unwittingly entered a time in the recent past (or future) that evening, so that he was then knocking at a time when nobody was in the house? I really don't know how else to explain it! 