are you able to remove the thermostat from the wall and sit it under your boiler to get the two items to resync again?
yes I have done that.
And it worked no better?
Ok, take the batteries out again and place under the boiler
Turn off the power to the boiler at the fused spur and leave off for 3 minutes
Turn the power back on and reinsert the batteries
Let me know what it does
ok every thing working