Hidden in plain sight in yesterday’s picture (right hand side, about halfway down) is indeed a jumping spider. Well done and welcome to the blog, Fen!
It is on a roof, but a very small one. This was actually the roof of a fibreglass box containing an outdoor power supply in the experimental grounds / greenhouse area behind the building I work in. By a trick of the lens it becomes a plain stretching off into the distance, all the habitat this remarkable and frankly rather endearing predator needs. As far as I can make out it is Sitticus pubescens, but I’m not that good at spiders so I’m happy to be corrected by more expert arachnologists.