Just had my Vailant combi serviced last night but shortly after the gas men left the light on the Honeywell HC60NG reciever began flashing red indicating a loss of comms. to the Honeywell CM61NG thermostat. I've tried re-pairing following the instructions but had no luck as the reciever doesn't pick it up. I'm still able to turn the central heating on through the reciever. Is it worth trying to replace the reciever (I can get a replacement cheaply) or is this a boiler issue?