A relative left house empty for ages. It was stressful but fine.
Insurance!
Council tax - you might be able to get a rebate on this? Not sure!
Mail redirection
Heating - either have thermostat set to a few degrees above freezing, heating on for an hour at coldest part of night. Or turn off water, drain system, and switch off boiler. Depends on how reliable your boiler and electrical supply is - if it’s likely to conk out then the pipes may freeze.
Windows - if you can leave them a tiny gap for ventilation that helps, but obviously needs to be secure & rain-proof. If you’ve trickle vents, make sure they’re fully open and clean.
Put bedding, cushions etc in plastic boxes. You can buy silica gel to absorb moisture - cheapest is to get that “swell gel” stuff meant for hanging baskets, or ask people to save sachets from packaging from shoes / bags etc.
Irreplaceable stuff - you need to leave it with someone else.
Paperwork - make sure you have photos of anything you need. If you don’t need it, shred and bin.
Leave appliance doors open.
Lights and radio on timers..
Mice - put plenty poison down against rodents. If it doesn’t get used, that’s fine. Obviously you can’t use traps. Even if you’ve never noticed any in the past.