So a cautionary tale. We installed a large (natural) xmas tree in our lounge ( also the room with the EvoController location) and since have had 4 days of intermittent comms failure with the boiler BDR91 situated at the other end of the house. , even though the xmas tree is well away from the line of sight between controller and relay. I have now moved the Controller out of the lounge and all seems well again.