Used all the suggestions found here to reset wireless connectivity (although indications were that that was actually ok) to no avail - Boiler continually displayed message saying the thermostat was set off although the thermostat showed on and requesting heat (black triangle). I realised it was most likely the receiver playing up but was advised it was a sealed unit that would need to be replaced if faulty. Last thing I tried before going down the new unit route was going to be short cutting the switch and whilst opening the unit I tapped the case and voila CH burst into life - it appears the physical switch mechanism had got stuck. So if you are in a similar position give the receiver a bash it may jolt it into life - it may save you £85.
Simon G
September 2012
howtomendit.com for free repair help, information and advice.
