One assumes this is an all-in-one cooker (Not a hob in a worktop and a separate oven).
If the rings are working OK then you know power is getting to the cooker. It all comes up the one cable, so you can ignore the electricity meter.
This may help you find the model number: http://www.indesitservice.co.uk/appliances/cookers-ovens/find-your-model-number/
One assumes you have two elements in the oven : grill and oven. It may be that you have two failed elements and didn't notice one you don't use very often. Its more likely to be something common to both oven and grill.
Are the oven and grill controlled by a single switch (cooking function) at any point? This, or wiring to it, may have failed.
You are going to have to do some detective work and think this through from first principles.
Consider getting a competent techie friend to have a look.
XXX
December 2016