She is a false widow, Steatoda nobilis.
They tend to stick to their webs, so are unlikely to be a problem in outbuildings, as long as you are aware that they are there. As winter comes, she will probably hide away until the Spring.
Thank you for such a quick response. As there is much talk and scaremongering in the news at the moment I am quite concerned as it sitting just outside my kitchen door, which is used (and door is left open) frequently at all times by children, pets and visitors. Is it ok to just leave her alone? I wouldn't want it taking up residence inside the kitchen!!
I cannot obviously guarantee that she will never venture indoors, heavy rain, predators...something destroying her web could see her displaced & on the move. However, if she has a little nook, or cranny to hide away in, this is where she is likely to bolt to in the first instance. She is not likely to want to come into an area where people & dogs are trampling past all the time...& even when S nobilis do make homes in porches & doorways, they tend to be up off the ground & out of the way.
I have a couple that live inside my front room window, they never venture into the room proper. I don't like them in the bedroom...not keen in the bathroom either, but if they have an obvious web in other parts of the house, you at least know where they are and can avoid them.
We have one over the front entrance to my flats, she is about 8" from the doorway & never ventures in, neither did the previous spider that lived there...here's the thing - if you do remove her, eventually another may take her place. If you try to remove her & fail to catch her, who knows where she'll end up?
Males can wander about more and are sometimes found indoors, but they will be less common over the cold months, as they die off...your female can't really be held responsible for them though.
All things considered, they are pretty docile and don't go around looking for people to bite...she's really no more dangerous than a bee that can't fly & likes to live in one spot? In fact, bees are actually more dangerous....