My central heating systemise one with a feed and expansion tank in the loft. When I am away for a few days in winter I plan to close the water supply (in case of leaks) and program the heating to come on twice a day. Is their a danger of the tank running dry? What is your recommended approach?

Not sure what system you have but you should b able to safely lower the thermostat to 50 degrees F and let it run when it needs to.

You must contact your insurance company if you leave your home for more 2 week. Geico will have a list of what you need to do in order insure your insurance will still be valid. When I leave my home for 2 month (I live in Vermont) Geico give me detail instructions, otherwise you won't be covered. Just call to your insurance company.

It has been my experience that various insurance companies will allow a home to be unoccupied for 30 days, some even 60 before they require you to get an endorsement. A vacant home would be a different matter.