Boiler timer sticks - just replace?

Replace your room thermostat with a programmable type. Then switch the boiler to always on. Ensure your hot water cylinder has a working thermostat, as this will be heated 24h, too.

Christian.

The message from "Christian McArdle" contains these words:

While I agree that programmable thermostats are excellent, the advice about the water tank is dependent on how the existing system is plumbed. Ours, like many, has a three way valve so the CH is independent of the HW in the first place so switching the CH by a timer/thermostat has no effect on the HW timing - though of course you'll need a new timer for the HW as well! It would cost a lot in gas to keep the HW on all the time even if the cylinder's well lagged.

No it won't, if it has a functioning thermostat.

Christian.

The message from "Christian McArdle" contains these words:

You tried it?

In my experience the boiler will come on every hour or so, which is wasteful.

Yes.

It will use very little fuel to do so on a modern modulating boiler, especially if the pipe runs to the cylinder are short. I have no qualms in running hot water 24h, and I'm relatively interested in environmental concerns.

In any case, if it is a problem, it is easy to stick a one channel programmer for the hot water.

Christian.

The message from "Christian McArdle" contains these words:

If the timer's that old, then it's probably not a modern boiler even though the OP says it's newer than the timer. Unless you use the hot water throughout the day there's nothing to be gained by keeping the HW enabled all day - and in some cases a lot to be lost.

Which was what I suggested.