My Smeg cooker has just started showing the same behaviour you describe. Oven fan is working, but there is no heat. I'm going to try replacing the fan heating element which you can buy on line from www.smeg-service.co.uk.
We can still use our oven in the mean time using the top and bottom heating element setting. I think there is also a setting to use the oven with the fan plus the bottom heating element which we have yet to try.
Good luck!
Graham., August 2006