Leaderboard

If the only practical issue (for now) is constant water heating, why worry? You won't overheat anything and the extra fuel used for HW (if your boiler controls are not limiting the 'on' time much during the day) will be trivial - and you have HW whenever needed. As I have off-peak electricity, I use an immersion heater in my cylinder for a couple of hours early morning as this is cheaper than using gas. The cylinder stat recognises that the immersion has done its job and merely tops-up with heat via boiler during 'on' periods. Sentinel X100 is fine - but I don't think worth the high price (unless perhaps in a new system when boiler manufacturer requires it).

The various co-operative societies traditionally give a 'dividend' (varying with annual profits) in the form of a cashback, based on members' purchase value over the year. It is still done (although I think currently in suspension because of the Co-op's recent 'trouble at mill') and, for regular shoppers, can be a tidy sum. Much the same as a Tesco Clubcard or Nectar Card. Wife and I rarely use local Co-op, but it is handy if passing and milk etc has run out. And the new TV I bought online a few weeks ago was much cheaper at Co-op Electrical than competitors - even without 'divvy'.

... and I thought AC/DC was something to do with transformers.

Are you sure valve is at fault? It is possible to get feedback from return in some systems. Is the synchronous motor working properly? I have three Honeywell two-port valves (HW; CH up; CH down - house has four storeys) at least 20 years old and all three motors have failed within the last two years. Easily replaced at about £8 each. If you do have to remove the valve, I suggest you inspect/clean/test it as it may well be good for another period or, if replaced, kept as a spare.a future replacement. £13.50 seems a lot for inhibitor, unless you have to use a couple of litres. I have drained into large containers and (after settling of black iron sludge) successfully re-used about 80% of inhibited water. Given that a drain-down or top-up is occasionally needed, the cheapest inhibitor does the job, especially in an old system.