David, I had the same problem. You need to change the element behind the rear inside panel. I changed mine yesterday. Partmaster sell an element for £18.97 inc VAT.
You only need a crosshead screwdriver and maybe a small pair of pliers to take the spade connector off the element terminals.
It's very straight forward to do. Try typing 'fan element replacement for Neff oven' into Youtube.
Make sure you have the oven electric supply turned off if you want to be safe. If you are not confident, call a qualified electrician.
Ray.
February 2010