Glare/reflection on the spider's abdomen makes the markings a bit tricky to see, but this is most likely the Rabbit Hutch spider (Steatoda bipuncta). It is one of our false widow species, but not typically recorded as a biter - file under harmless.
Have a look after dusk, they're pretty good at concealing themselves during the day in cracks, gaps & vents. If it was a female & established in a web it may not have gone far (assuming it hasn't been driven out by bad weather etc.) Males (smaller abdomens) wander by nature, if he was there & gone, there's not much cause to think he'll be back.
I get S. nobilis, S. grossa & S. bipuncta indoors, they're much less of a cause for concern compared to the popular perception.
It was definitely a female. The abdomen was pretty big and rounded compared to the head and legs.
As for popular perception, I totally agree. The media blew the fake widow story out of proportion, just like they did about ten years ago, instead of telling people that 5 (I think) species are native to the UK.