Is it my thermostat? ?

Good afternoon.
I have a drayton RTS1 Thermostat in my 15 year old house. The dial on the front has been loose for some time and falls off from time to time.
In the past month, the thermostat has not kicked in to turn off the temperature and the heating is on full power all the time. The dial clicks when turned to indicate it has been turned below the current temperature (as if to switch it off) but the radiators stay on.
Would changing the RTS1 dial unit for a new one solved this issue?
Thanks in advance
Jamie

Jamie Ball
January 2013