electric oven not getting up to temperature?

hi there i have a electric belling xou176ss
i have 2 elements in this oven,
when i use top element (not grill) it gets warm in the oven but now where near the heat it should be,
but when i use top and bottom element it then gets up to temperature,
so iam guessing it is the top element,
but i phoned up someone from the yellow pages and they told me if its getting warm it cant be to top element it must be something else,
iam also guessing it cant be the thermostate because the stat is working,
i have also tried to search on the net for details on where i can find the bottom element and have also pulled out the oven and i cannot find any access panals to see the bottom element,
is there and easy and better way to find out what is wrong with is, or does anyone know the answer,
thanks for now,
mr taylor