What bug is this? Manchester, UK
That looks like what I would call a "daddy long legs", also known as harvestmen. These are arachnids of the order Opilones. There are some 30 species of harvestmen found in the UK. The webpage https://harvestmen.fscbiodiversity.uk/ has a very useful identification tool and based on it, I believe your photograph shows a Leiobunum sp. A:



Please visit the site itself for more details as it doesn't allow copying.