Thanks guys. That's what I suspected then. My roomstat in the hallway is actually not that old as the last one broke and I simply replaced it with the equivalent new, basic dial-type Wickes one as a temporary measure. I'll replace this with a digital one when I do the programmer.
The main...
Chaps,
We've been in our house for a couple of years now and it's probably time I looked at replacing my aging CH controller. The system is a fully-pumped affair, with a conventional boiler downstairs, cylinder upstairs (no immersion), wall-mounted stat in the hallway and this thing upstairs...