flashing zeros + auto sign and oven wont come on. What can I do?

I tried to change the time (British winter time 1hr earlier)on my Belling Format after I had set the automatic cooking on/off time and now I cannot operate the time. I swtched of the electricity and now I am left with 3 flashing zeros and the auto sign.
I have tried switching the electricity off and on but it remains the same, and the oven will not come on. What can I do. I do know how to reset the time and the cooking time but this is different. I have the operator's manual but it doesn't cover this.