Thanks plumbersmate1! Took the head off, something unclicked, put the head back on and now the manual-auto switch actually works. Heating comes through on the auto setting.
I didn't spray any WD40 on, as it came free straight away. Would you recommend spraying some in there anyway?
Have an Altherma SpaceAir heating/hot water system. Just tried the central heating for the first time in months, but the radiators do not heat up, no matter how high I make the temperature.
Compressor and heat pump both turn on when the heating is switched on, however no hot water reaches...