These are the Common Garden spider, Araneus diadematus, a common and widespread species. You would be hard pressed to find a garden without these in residence. Females, as this is, are at their largest in the autumn and are laying their eggs in silken sacks about now. The female sits with these to protect them for as long as she is able, but succumbs to the cold and lack if insect prey as winter sets in. Her eggs will hatch next spring.