the element in the top of my electric oven needs cleaning - when I use the grill, the fat spits up and coats the element, but the 'muscled man' foam cleaner I use for the rest of the oven can't be used on the elements.
Have you still got the instruction book that came with your oven? That should tell you - or phone/e-mail the makers of the oven, they should have some ideas. Good luck