I have a baxi 105 HE with integral 7 day timer - but I cant set timer?

I reset the timer and when I come to programme, the numbers 1-7 keep flashing at the top and will not stop.
The only thing I appear to be able to change is the time, but that will not set the clock or move me onto the next stage.
I recently moved to this house and have all the instructions which I was following, but I seem to be frozen, and am currently having to use manual override for the heating.
I have set this once before and was just intending to adjust the times. Has anyone else had this problem and do you know how to overcome it.

Kath Ridout
November 2012