I'm in the south east UK. I have a site I'm doing intermittent timber work on, that's been left idle for much of the summer. When I came back it has huge webs strung from walls to beams and across the open spaces, everywhere, with the spiders in this picture sitting in them.
At a a guess they are about 30 - 40mm across (maybe 25 when 'sitting' with legs curled at rest close to body?). They sit in the middle of the webs, not hidden at the edges. The webs are quite strong and look like they are durable, as webs go.