Webs criss-crossing your garden are not going to be false widow spiders, but are almost certainly garden spiders Araneus diadematus, an abundant and highly visible spider at this time of year. These are harmless to humans and occur in almost every garden in the country.
There are a number of Steatoda species found in Britain, all so-called 'false widow' spiders. Three are possible in or near buildings, S. bipunctata (very widespread, probably occurs in almost every building or outbuilding in the country), S. grossa (widespread and sometimes very frequent in the southwest, but becomes much scarcer further north and east, but in the last few years seems to be increasing) and S. nobilis, the one which gets the press for biting humans (originally confined to the south coast, now increasingly turning up elsewhere in southern England and found in 2006 in Barry, S. Wales). Steatoda nobilis has on occasions been responsible for bites, even though many of the cases publicised for this are almost certainly due to another cause. It is extremely unlikely indeed that your false widows would be this species, since this would be a very long way north of any reliable records of this species.
I can't tell which species of false widow or other spiders yours might be without the actual spider or a reasonable quality photo which shows to upper abdomen patterns.
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