Heating timer problem

[drchasuble]

I had a Honeywell combi boiler installed in 04 and a wallmounted heating timer box with "British Gas RC2" on it was installed at the same time.
Despite me asking BG time and time again we never got instructions for the timer doobry. It was always a case of it's in the post or we don't supply instructions for that item.
My Dad managed to work it out and the heating worked perfectly well.
I needed the heating on earlier than usual last week and reset the timer. Now the heating is either on or off all of the time. I have to do it manually.
BG apparently can't get anyone out until mid Feb and my Dad is away.
Could an able ABer assist me?
Many thanks

Doll