it sounds as if you need to replace 2 enrgy regulators (switches) they are approx £15 each. To dothis you will need to remove the contrl panel,side panels&hob.
Tdo this;
1. TURN OFF POWER
2. If clock is still iluminated you have not turned power off ,
3.remove control knobs by gently pulling off
4.remove the 4 screws under the panel and at the top of the top oven
5.remove side pannel (6 screws each side) 3 at the back 1 in top oven 2 in mainoven
6. remove screws holding hob 3 eachside (1 black one on side of contro pannel 2 silver 1at front 1at rear of hob unit)
7.gently lift hob and slide back about 4 inches
8remove 2 remaing sceews on control pannel 1 each side
9slide out control facia and remove temp .indecators from damaged switches
10remove 2 screws from cover on topof stove to access the energy regulators
11.replace regulators
12. reassemble in reverse order
W . Hastings, May 2008