However, you seem to have extra wires connected.
Do you still, perhaps, have an old programmer still in place but permanently set to Heating On - or an old thermostat similarly set or its wiring connected together?
I think that there might have been an old wired thermostat there before and they have just connected the wires together.
As it is, all you have to do is fit the Hive to the backplate (although you may want to use the new Hive backplate).
Whilst this will work as before, it is a bit of a bodge leaving unnecessary live wiring in place.
When you have removed the RF2 post a picture of any wires behind it and then you can reconfigure the backplate wiring and disconnect redundant wires.
the wire behind the RF2 is dead.
It has been disconnected over 13 years ago when we had the combi boiler professionally fitted .
I have enclosed 2 photos of back plate and the dead cable in the wall.
The system now up and running.
Thank you for your help, very much appreciated .