I found this spider inside a computer in Basildon today. My first impression was that it might be a false widow as they've been in the news a lot recently. There was a smaller dead one inside the computer too and quite a lot of web. I did call the NHM identification number and spoke to a helpful chap to suggested emailing a photo in or even sending the specimen itself, but I misplaced the email address so figured I'd ask on this forum.
I do still have the spider as some of the office staff were planning on killing it and didn't think that was necessary. It hasn't bitten anyone, and I don't even know that it would cause much harm even if it did. To me, it's just a cool looking spider.
If anyone is able to confirm what it is, I'm happy to release it back into the wild (although not in my house if I can avoid it!) so it can do what spiders like to do best.
The body is maybe 10-12 mm in length. I've included a photo and video to help you out.