The ZA6's are the newer removable head ones. Clip the lever over to the open position, and then press the black button on the side to release.
It's the ones that started 679H or 779H and badged ACL Lifestyle instead of Drayton that were non-replaceable.
Unlikely to be the Digistat 3 unless the programmer has gone aswell - as the live to the thermostat comes from the programmer - so no live to the thermostat = no live for the thermostat to send to the MV.
Is it a S-Plan system by any chance? If so I'm guessing a stuck microswitch in the M.V...
no,
A timeswitch is a single channel unit, usually used to control your heating from a combi or to control an extra heating zone.
A programmer is a two (or more) channel unit, usually controlling heating and hot water.
24hour vs 7day has nothing to do with it, neither does number of on/offs.
Yep
Dunno about regs, but he would not want a programmer with a combi. If regs stated times of 'off' (i.e. not just 5C setting on a prog stat) were needed, he would need a timeswitch (not a programmer) as well.