All spiders bite, its how they kill and eat. The reason most UK spiders don’t bite people is they do but their fangs are either too small or wrongly shaped to pierce the skin. As most native UK spiders are small there are very few reported bites.
Also all spiders have venom. Though most UK spiders would be pretty harmless to humans. You will probably experience slight swelling, soreness, redness at the swelling etcetera. I have heard of a mild fever from a false widow but have never seen the reports so couldn’t be positive.
The only time to be concerned would be if you are allergic to the venom. Similar to people who have allergies to bee stings. So if you get bitten just be observant.
On a side note false widows and many other spiders will not bite unprovoked. They are not particularly aggressive or even defensive and biting would be their last choice.
I would much rather be bitten by a UK spider than someones cat, dog, hamster, gerbil….
If you do get strange swelling, colouration etcetera could you post some photos?
real black widow will still be attached to you when it bites as it doesn’t retract it’s fangs after biting
I think thats a myth.