No Grill operation for stoves 720ef

First things first. The top oven lights ONLY come on when the top oven is switched on. Operating the grill DOES NOT turn the lights on. If you wish to see what you are grilling, you have to turn the top oven control knob on to its first position as well as turning the grill on.
Secondly, the grill only works when the door is open. The grill does not work when you shut the door. When you open and shut the door, you should be able to hear the microswitch operating. It is located in the right hand side of the cooker, between the inner and outer panels - you cannot see it. I haven't seen the switch first hand but they normally come with an arm that contacts the door mechanism and the door mechanism operating, causes the arm to move, which causes a button on the switch to move and make the circuit. It has been known for the arm on the microswitch to bend with use so it no longer works correctly.
If you have checked all above and you hear the switch operating, then it could have failed. They are quite common, so if you can't get one from STOVES, try espares or someone like Maplin or RadioSpares.
The get to the microswitch you have to take the oven out of the housing and then take the right hand panel off. You should then be able to see it and check its operation.
All the best

First things first. The oven element is totally separate to the grill element. The clock has to have a time set for either the top or bottom oven to work, whereas the grill will work without the clock being set.
The control knob for the top oven is the ONLY control that will turn the top oven lights on, the grill does not turn the lights on. ( If you want to watch your toast, you have to turn the top oven switch on to the first setting as well as operating the grill control).
To prevent the grill being operated with the door shut, there is a micro-switch on the door hinge that allows the grill to operate ONLY when the door is down. The grill control also does not illuminate unless the door is down. There are two options on the grill control - right or left. One way is the inner element only and the other is both inner and outer ones.
So if you have done all that and it still doesn't work, then the micro-switch could be faulty.
Best of luck

First things first. The oven element is totally separate to the grill element. The clock has to have a time set for either the top or bottom oven to work, whereas the grill will work without the clock being set.
The control knob for the top oven is the ONLY control that will turn the top oven lights on, the grill does not turn the lights on. ( If you want to watch your toast, you have to turn the top oven switch on to the first setting as well as operating the grill control).
To prevent the grill being operated with the door shut, there is a micro-switch on the door hinge that allows the grill to operate ONLY when the door is down. The grill control also does not illuminate unless the door is down. There are two options on the grill control - right or left. One way is the inner element only and the other is both inner and outer ones.

First things first, the grill only works with the door down. Directly you shut it, a microswitch operates and shuts the elements off. ( Of course the top oven operates with the door shut).
There are two options for the grill. Turning the control switch to the left operates the inner element only. Turning it to the right operates both the inner and outer elements together.
With either option, setting 5 (the max) has that option on full, whereas settings 1 to 4 switch on and off.

There are seperate thermal (overheat) cutout devices for both the top and bottom ovens. First check to see if the lower oven fan is running ok and is not restricted by grease or fat (there are 4 self tapping screws that hold the fan cover on) and the thermostat is switching off and on as it should. You should also check that the main background cooling fan is running and switches off a few mins after the ovens have turned off. If these check out ok, then it is possibly the lower oven thermal cutout.

I had problems with tripping and it was a faulty RCB on the consumer unit. But it wasn't just one appliance causing the problem.
Have you isolated it to the top or bottom oven. If it is the main oven, then it could be anything associated with the operation of that component, i.e. the oven control knob,the oven thermostat, the element, the element fan, the overheat thermostat all could have insulation that is breaking down that could cause this problem.
Before you go and buy anything and if you have the time and patience and confident enough and know what you are doing, I would remove the oven from the cupboard, take off the top and back covers, note the wiring for the element, take the leads off the element and run the oven with the element disconnected and see what happens. That should prove whether it is the element or anything else.
BE CAREFUL.

Not too sure of the model, but on the 720 the grill will not operate unless the door is down (microswitch control - you can hear it operate when the door is shut/opened) and the overheat device has not operated.(Cooling fan has to be running)

No, there is no reset button. However, the grill will only work when the front is down as there is a microswitch which operates to provide connectivity when it is in this position. This is to stop the grill overheating. The switch could have gone faulty.
Does the top oven work ok?
When you operate the grill there are two options, part or full. Are they both failing? Does the cooling fan switch on when either grill is operated?

there is a safety stat/fuse on top of the oven exterior i think you will find that it also has blown. Make sure you have isolated the appliance at the fuse board first though, Good Luck

The grills appear to be independant of each other. Does the oven still work and the oven light come on?

Depending on your answer it could be that the Top Oven Switch has gone faulty. The Grill Regulator and the Switch work together on the top oven. To get at both you will need to take the top of the oven off.