As it's quiet in here.
Around 7:30 this morning I thought, it's cold, I can't hear the boiler or the pipes creaking. Went downstairs in my jim jams and the wall stat display was flashing on and off, which indicates batteries flat. Replaced the 2 x AA batteries and it came on but it not only lost the time and date it had lost details of the 4 x time zones P1 to P4.
It took me a while to set it up again and it isn't warm yet!
I have 2 x £11 Chinese clocks which have built in web servers so they can be reset, be nice if the stat had he same although I suppose changing the batteries when the clocks changed would have done the trick.