It'll most likely be the thermocouple. Mine has the same problem. I was searching to see how to change it. Remove oven shelves and look at the burner you will see to little metal spikes overhanging the flame area the one on the rhs is the thermocouple. Take the rear of the oven off and you will see a thin copper pipe connecting the thermocouple with the oven switch at the top. This whole thing can be bought for about a tenner. My issue is how to remove the connection at the oven switch. i am sure the hob lifts up but i dont know how???
steve, November 2013