Not easy to say from that pic, but a male Steatoda nobilis is a possible candidate. Google some pics, if I'm right, tip him outside. They're not aggressive, nor actually dangerous, but males do wander about & can end up in odd places (females are more sedentary, nevertheless many prefer them outdoors rather than in too).
They don't live in nests/colonies, so if this is the first/only one you have seen, you're not necessarily likely to find lots more...I actively look for them & only see 1 or 2 males a year, of this species.
Thank you very much I just looked at pictures online and it did look like it! This is the first one I've seen like this in the house that's why I was curious, he has been given a new home outside :D there seems to be a lot of hype around them in the uk media.