Check up in the loft mate ... If they are thinking about coming in, they will be coming in around the eaves somewhere. 3 or 4 every day is the usual sign.
I had one a few years ago .. made a small football-sized disgusting looking nest, just laying on the insulation in the loft.
Just waited til it was cold and dark, dressed up well, went up the ladder and put a sheet clean around it and stuck it in a binbag.
Next day chucked the whole lot on a fire. Few crawlies left in the roof .. spray, and block the hole.