Apparently the UK is « bracing itself » for a cranefly invasion. So far I have found two bouncing around the porch light and this one resting on a shrub.
A damp winter and warm September have provided the perfect conditions for this insect and there could be billions of them. They are considered an agricultural pest as their larvae eat the roots of cereal crops. However, they do not bite, sting or spread disease so there is no need to be scared of them. They just make a really annoying noise if they are bouncing against your lampshade at night. They are also known as « daddy long legs ».