wireless relay

Hi all, I have an outdoor light which has a titan receiver relay (as in the picture) and this is controlled by a switch indoors as in the pictures. However the receiver has now packed in and I need a new one. I can seem to find that specific receiver anymore so wondering if anyone can recommend...

I wish to install a new wireless thermostat. I can place the thermostat wherever I want but the wireless relay needs to be connected to the boiler. Currently, I have a wired thermostat which is connected directly to the boiler. All the wires arrive into a junction box just below the boiler...