This is the second one I've found by my back door, the first one clung to my jumper when I brushed past the door frame, is it a false widow ? My son likes to pick bugs up he finds in the house and make them beds in the garden ! Although we used a glass with with one !
Fear not, this is Zygiella x-notata or the missing sector orb-weaver spider - very common and harmless and often found around buildings, particularly window frames and sills, porches, sheds, etc where they make their orb webs. Usually the spider is in a retreat close to the web, emerging when it senses something has been caught.