It turns out that doggo (who goes mad at any intruder) has left some of her treats in the garden and the badgers come around at night and eat them up.
Tonight there were no treats for one badger as I had watched an older badger hoover them up.
Some time later (at about 00:45) a younger (well smaller anyway) badger comes up to the bi-fold doors and raises itself up on the sill. When it sees that I have noticed it, it proceeds to the bi-folds in the kitchen and moves its snout to the ground several times.
Now I know I am anthropomorphising the badger's behaviour but it did look as if it was gesturing for food.
I opened the door, threw out a treat which it picked up and disappeared with.
You can if you wish continue to feed the badgers, maybe put up a trail camera (they are very cheap now) but as you have a dog - a smallish dog I seem to recall - remember
The Badgers have fleas and ticks, those front claws are awesome and an adult Badger will happily rip a small dog to bits. Plus if your dog is like mine, it will be rolling in badger poo in a heartbeat.