Yes it is probably the cooling fan.
We have had our cooker for 19 years and i have changed the fan about 4 times.
Same symptoms, control unit goes off until cooker cools down.
If you can turn power off, it is easy to get too.
On right hand side at top and I bought my replacement from Maplin. They sell metal cased fans for a fiver.
Local electrical repair shop wanted 50 quid for part.
Andrew
November 2008