This morning I have looked out of my window and over the garden is scattered lots of little bits of polystyrene from the wall insluation. This has never happened before. Could it be caused by the strong winds? Or could this be sign of mice/rats?
I haven't heard any noises but I'm very worried. I've noticed that there is a big gap at the bottom of my electrivity meter box, and then a hole into the wall where the cables go. This seems to be the only hole in the wall where anything could come from.
Yes it's caused by the strong winds recently.
Find out where it is coming out of and stuff something into it - newspaper, perhaps, if it's a sizeable hole.