My Belling Cooker Format 625BH oven keeps cutting out randomly?

Oven cuts out randomly and I have to switch power off to restart it. Also, when the oven is on for a while a loud pitched buzzing sound occurs. One of the hob rings when switched to 1 will give the full heat as if it was set to 6. Also have crack in glass top. Otherwise works perfectly!! Am using oven at the moment and no problems but could be using it tomorrow and might cut out. Any solutions or do you think would cost too much to repair all these faults.