Hey Jeza, what a nightmare for you. I am really surprised you haven't found any droppings though. When my sister had a mice infestation, she put clean bedding on and when she went up after about an hour (this was in the day), there was a dropping in the bed. Mice are very clever though as she had traps everywhere baited with just about everything and she never caught one.
I think it's a good sign you've not found any droppings so far. Anyway, sorry I can't offer any advice but I've been thinking of you, wondering how you were getting on as I know it's down to you to sort it. Hope you're ok :)