Just a note to those considering buying a programmable thermostat and
deciding on the make to buy.
I've just bought the Sunvic one from B&Q. At 30 quid, it is much cheaper
than a Drayton Digistat 3. Rather than programming with the normal 3 on/off
times per day, you can set up a heating profile with 24 dots representing
the hours and have complete freedom to set the dots (i.e. up to 12 periods
per day, if you are weird). You then set each day to the profile previously
set up. (There are 6 factory suggested programmes too). You can set each day
separately, or set 5/2 or 7 days all at the same time as you wish. You can
set both the 'on' and 'off' temperatures. It has logic to pre-empt the onset
of an 'on' period (but no external temperature sensor).
It displays the the time, call for heat, the day, the temperature and the 24
dot profile at all times. Although slightly bigger than the standard light
switch size, it only sticks out of the wall by a relatively small amount and
looks very classy. Much less intrusive than other makes. It also has 6
buttons, making programming much easier than those with fewer buttons. It
even has a electroluminescent backlight and manual override (both programme
advance and temperature adjust).
In use, it keeps temperature well within 1 degree at all times. Very highly
recommended and much better than the Drayton Digistat 3, IMHO.