Ok, so probably not a badger, but something is doing an awful lot of scraping and digging. Sounds definitely too big to be mice, and wouldn't have even thought a rat could make that much noise.
Called the council's pest control, who put out rat poison. He said 'we don't deal with squirrels, so I'm going to say it's a rat. . .but this stuff will kill squirrels too' and winked.
It's been two weeks, and no improvement. Only happens on one side of the house in the first floor spare bedroom, and I can also hear something that sounds like it's inside the cooker hood (same side of house). Could it be in the outside wall as well?
Am really starting to think it is squirrels....how do you get rid of them? Can't even see how they'd get in!