Are there different settings that you can use. My oven has a dial that you can select just the top element (or the bottom one). Also, is it fan forced? The fan should be distributing the heat a bit more evenly so maybe check that out.

Also, this may sound a little silly but is it possible that the element at the bottom should have a cover that has been removed at some stage?

My Mum also used to put paper under fruit cakes but she used to use several layers of baking paper and that was in a slow combustion oven where the fire box was below the oven and so that is where the heat came from entirely.