Don't know about Dormice Martha but the 'ordinary' mice are starting their annual migration into my house now it's getting too parky outside for the dear things. My missus says they put their hobnailed boots on at night but being a bit mutt I fortunately can't hear them. I've tried all types of electronic deterrents which sort of work for a while & then get ignored so I've abandoned the idea of keeping 'em out & now concentrate on trapping them. I also don't like using poison in the house for the same reason as Martha. The new generation of pre-baited plastic traps seem to work here & at least one can chuck the cadavres before they start to stink :-) If anyone has any recommendations I, like Martha, would be happy to hear them.
mmm… long winter ahead too 
I have caught around 150-200 Loire since buying our house in France about 10 years ago. It had been empty for years and Loire had taken over the roof space. Catching them is easy if you have access to and sufficient space in the roof. I use a humane animal trap/cage about 2 foot long by 1 foot and bait it with freshly peeled apple just before dusk when they start to emerge. They cant resist the smell of the peeled apple. Once caught they are taken about 3/4 miles away and dropped off in a wood. They can get in the house via small holes or in our case by crawling under the tiles and finding/gnawing holes in the wooden slats below the tiles. Once inside they wreck the roof insulation for nesting. Not had any problems with gnawing electric but they have gnawed the water pipe insulation. Have now wired all the entry points around the roof to help prevent more getting in but still catch a few every year and no idea where they are getting in!!!
I expect they are wondering what you are doing in their home.
Give them the wherewithal to make their nests and they won’t mess about with your insulation.