I want to replace my existing mechanical room thermostat with a digital 5/2 programmable room thermostat.

My current mechanical stat has three wires connected to it, live, neutral and earth. I have a combi boiler which has a 24hr timer control on it in addition to constant and off settings.

Can I just replace this mechanical stat with a digital programmable one or am I missing a Switch Live, therefore needing the services of an electricial?

Sorry for the dull question!

no your not missing a sw live you are missing a neutral. don’t be fool by the colors of the cable you will need to run a three core and earth back to were your cable comes from. the old thermostat is a switch but the new one has a relay in it for the switch to work it gives it better control

Ok. Are these existing wires likely to come from my boiler or my consumer unit do you know?

the cable will go back to the boiler or a joint box beside the boiler

They would come from the boiler because that is what is switched on & off by the stat unless you have an additional controller in between (some Potterton boilers do)

Ok, I can see those wires now. This is probably a job for a spark but thanks for your help, it’s good to know what’s involved though.

you in edinburgh ?

nope, near leeds