I put a grand piano into storage on its side in a friend's garage in Cheltenham yesterday, and found a few of probably the same (or similar?) of what you've found Mark between some boxes and the wall at just above ground level - they didn't seem to like the light much and fairly slowly went to hide in darker places. There are supposed to be quite a number of "false widow" spiders about in the Cheltenham / Gloucestershire area. I - and no doubt my friend whose garage it is - would be very glad to have some fairly positive identification on these please. Am I right thinking this is a type that can give people a hefty bite (a bit similar to a wasp sting)? I'm not keen on some of these coming out of the piano when it's being played after storage! And I need to give my friend pointers about what she could/should do about them - presumably the NHM advice at the following link applies?
The ones in my friend's garage are about 2-3cm across (approx. size of a 50p piece). The fibrous background in my photos is course flooring tiles on the garage floor. Spider body colour is dark-reddish: