DeLonghi DFS903 problem?

DeLonghi DFS903.

When we turn the oven switch on (even if its just the light position) a wired sound comes from the oven. The sound builds up to a peak, the starts again.

I've managed to get the top off and under the gas pipes there appears to be a cylinder shaped fan, under a cover. The sound is coming from the fan. The fan doesn't spin as the sound builds up, when the sound reaches it peak the fan starts to move, then stops and the process starts again.

Obviously the fan needs replacing, but, is it a fan, what is it called, is there a part number for it, do the gas pipes have to come out to get to it, etc?

Cheers