Out of the approximately 650 spider species found in the UK, nearly half are from London. None are too dangerous, regardless of their reputation. Though people are bitten at times, British spiders are not normally strong enough to deliver a proper bite. Their venom is also weaker than most biting insects.
Common Spiders: Common Garden Spider, Long Bodied Cellar Spider, Common Wolf Spider
While the venom of any of these spiders is not considered deadly to humans, the woodlouse spider can deliver a powerful bite that stings.