We've got a Digistat SCR system. The RF1 unit has packed up. I also read that it has been discontinued by Drayton and replaced with a Digistat 1 (that has a more conventional dial control). Can I buy one of these and use it with the existing receiver or do I need to replace both reciever and thermostat? If I have to replace both do I need an electrician or is it a simple job?