We have hedgehogs visiting at night too and provide hedgehog food for them - plus water I hasten to add, in a separate dish. They are delightful little critters if somewhat mucky in their habits! We have a lot of places they can hide in but we've also got a 'hedgehog highway' through to next door. The man who put up a new fence for us suggested it and there's various ways these animals can explore the gardens on the other side too. If you come across a hoggie in daylight it's not good news and if you can, take it to a hedgehog rescue centre as it's likely it will need medical attention
To think that London, or anywhere else for that matter, does not belong to any one demographic