i have same problem with the same oven
pulled oven out and sat it on a bucket turned it on (after it came back on ) the fan trembeled and buzzed but didnt turn
looked on a few forums and they all said that due to it being a GAS oven you need an approved repair man (gas safe registered)
which is a bummer cause i am an engineer and can easily do the job but i am not certified (certifiable yes heehee haahaa hoohoo) just not allowed to do it
i would think that the fan is easily found and fitted
but i will look for more advice for myself tomorrow from a man that can
i will come back with more info when i can
Gavin McCrae, December 2010