Awesome. Thanks. I think I spotted these before but forgot about them.
I think I’ll pay the extra and order from Amazon prime. 
I also note they do battery powered window/door sensors that can be hacked to signal when the wires that used to connect to the IR sensor are contacted. These would be handy for another part of my heating project; which is to heat the living room alone with the electric wall heater, but only if the doors are closed which usually means I’m in there. (Still have to decide if I modify the heater to gain access to the push buttons or if I try and use a combo of a SOnOff relay and an IR sender, the heater only pulls 8A on max, so the SOnOff ‘should’ be fine. I’ll need to check in rush).