Thanks for location. This looks like Steatoda nobilis, the so called 'noble false widow' It is the one which gets into the news, but you can get sensible information at look at false widow spiders, http://wiki.britishspiders.org.uk/index.php5?title=False_Widow_Spiders
and http://www.buglife.org.uk/bugs-%26-habitats/spider-bites
.


It is widespread and frequent in your area, and has been for a great many years, so should be thought of in the same way as social wasps and honey bees.