Combi boiler and programable thermostat

[steveb8189]

Am in the process of refurbing my house and I have a 15 year old Worcester 240 combi boiler with a mechanical timer on the front of it and a basic room thermostat in the hall.

I want to change the thermostat to one of the fancy programmable ones - read some comments on here that the honneywell ones are good.

What I don't know is what to do with the mechanical timer on the front of the boiler. Do I just set that to always on and use the programable unit instead? Will that cause any problems?

Any help is appreciated!