How to fix my Belling db2 main oven?

The above mentioned oven "Platinum db2 Ser No.03 001463 Cat 2H"Has worked fine for many years,sudenly the main oven has stopped working.
There is no gas getting to the oven burner rest of cooker working fine,all rings,small oven and grill.
The timmer clock is flashing 0000 auto?
Any advise as to what the problem might be greatly appreiciated

Bernard
June 2011