This is not a False Widow but a Black Orb Weaver or Walnut Orb Weaver, Nuctenea umbratica. These spiders occupy their webs at night feeding principally on night flying insects - so moths feature quite heavily. They are known to bite if they are trapped between skin and clothing, which happens very occasionally when people demolish sheds or fence panels. They are a common and widespread species found in all gardens, but hide away in crevasses during daytime.
So all things considered ... best described as harmless.
As for living 5 mins from the coast in Ceredigion - I think you'll find that that bit of coast is getting closer to you by the day ;)
Wow, thanks for that reply.
I was convincing myself it was a false widow. But know they are frequently misidentified.
Out of interest, what would be the main differences I'd be looking for? Would a window have a more definite cream blob on its body rather than the few cream dots on this one?
Thanks again for the info.
And yes you're right, the coastline seems to be getter closer to us by the day!
To see the main differences you could do worse than look at the photos on these links:
Your spider Nuctenea umbratica has a more flattened abdomen, which allows it to tuck itself away by day in crevices eg. between fence panels. The dark patch on the abdomen has a noticably wavy edge where it meets the lighter surounding colour, although the contrast between the two colours can vary.
The false widow abdomen is a bit more bulbous in shape. You're right in that the false widow has a central lighter marking on the abdomen surrounded by a darker area, although the shape and extent of the lighter patch varies - it sometimes looks a bit skull-like. It also has a prominent light band extending around the front of the abdomen and reaching along the sides. Hope that helps.