We’ve had our place in Brittany for just over a year. Its a stone longere with one or two of the usual jobs to do - including repointing pretty much all the outside walls! Until we’ve been able to do that we are obviously going to be vulnerable to mice coming and going as they please. I would set traps or lay poison but as I’m not there to empty the traps or replenish the poison I don’t think this is an option. I think the previous owners tried a plug in electronic device to deter them but, judging by the fact that I found it dumped in a box of other junk in the garage, I’m guessing that it wasn’t too successful. Anyone got any good ways of controlling mice when you’re away from a property for a while?
I presume you mean this sort of thing
No suggestions beyond using bait/poison - which has the advantage that they normally die away from the house.
I have the same problem as I have realised in the last couple of visits that they are getting in the cellar - not much I can do except try to make it “rodent proof” but I don’t think that will be possible.
We used electric ultrasonic devices in UK… and found they worked amazingly well…for rabbits … and indoors for mice…
brought them here to France… and they seem to be keeping the rodents away from the areas they guard…
they are about 30 years old… so very basic… but… they work… 
We put a very fine metal mesh (quite sturdy) in the openings/ventilations to the cellar… light and breeze gets through but not much else…
Rodents move within the walls from roof to all over… so the electronic bits are strategically placed to protect certain open areas within the house… lest the rodents feel tempted to explore.
All internal doors close very flush and if we are away/out for a period… I keep them shut…
We live in the countryside and I enjoy the wildlife… in its proper place… 
We have a constant battle with mice.
These are very good (up to 8 mice per night! Screwfix link
But you need to be there to empty the traps, so we are also trying one of these: YouTube video
When living there permanently we will be getting a cat!
What is attracting so many mice into your house in the first place… perhaps you should answer that question… and you might find the solution… 
Yes, good point! We went over our cave/larder with a magnifying glass and sealed every tiny crack. Since then we have had few problems with mice and the ones that do come in have been birds of passage just taking shelter in the worst of the winter.
By far our greater problem is stone martins getting into the insulation in the rooves.
In the UK we had birds wearing jackboots , thundering overhead… until we found and closed their “front door”…