i have worcester 28 cdi and it has a siemens rdj10rf wireless thermostat, it has never worked very well range to lounge from boiler too far, now its stopped entirely, want to replace with a standard hard wired thermostat. questions is it a job i could do? what thermostat would be best, i laid some wires when i did house just in case (one was normal power cable one 3 pair tele cable) are they usable?is there anything i should know about disconnecting wireless and putting in new? cheers jon