Connect to existing wireless receiver
I have searched this forum and looked at installation videos and general searches. It seems that despite many heating systems having wireless thermostats for turning the heating on and off, via a signal to a receiving box wired to the boiler, your system requires replacing this receiver with some slightly scary rewiring. My suggestion is that you tie into the existing various manufacturer protocols and have us take the batteries out of our old wireless thermostat. This would surely make this common configuration significantly easier for novice installers.