This is a female Steatoda nobilis, a false widow species. They are able to deliver a bite to humans, but this very rarely happens. Females tend to stick to their webs, are docile & non-aggressive. Problems can occur with wandering males finding their way into places they shouldn't, but again, they tend to avoid contact with humans & possible threats...they are not particularly brave, even as far as spiders go ;-)
I have a pair, including a very large female living over my front door. I also have a female in my living room window vents. She never ventures into the room proper, hardly moving a few inches from her hiding place. Males, I tend to scoop up (in a soft plastic cone made from a cut down pop bottle, with the lid in place) & relocate them. I have one in a jar next to me right now, that I teased out of my shower.
I'd be aware of her, just to avoid possible accidents with family members etc. but I wouldn't be any more concerned than if you saw a bee in the garden. I stayed in a resort in the Isle of Wight where every chalet seemed to have a few S. nobilis living in every bathroom window. They don't seem to make any impact on business there! ;-)