Hugo Nebula wrote:

I'm leaving for a new job 200 miles away. I haven't yet sold my
house, so I'm going to have to leave it empty for a while. What
should I do with the central heating? It's a standard boiler fed from
a header tank, with a pump, radiators, a hot water tank and a
three-way valve.

I presume turning everything off entirely is not a good idea?

I thought of leaving the heating setting to 'On' permanently and
setting the room stat to low, just in case we get a late frost.
Should I also set the hot water to come on for a few minutes, just to
keep the three-way valve turning, and also to ensure that the boiler
does fire up at least once a day?

With the C/H running, I can't turn off the gas or electric. What
about the water?

I had this prob when selling me mums (empty) house.

We left the services all connected and the CH coming on for an hour a
day in the wee small hours (coldets time) to prevent frost damage and
damp build up.

The water was left on, but you can get a reduction in council tax and
water rates for unoccupied premises.

The gas and electricity are metered anwyay, so you just get a rebate or
a low bill when the meters are finally read.