We have the same oven. Sounds like it probably just needs a new fan, contact Stoves direct to arrange for a visit and repair. I believe they charge a total of £80 (no matter how many times they need to visit to complete the repair), plus the cost of the parts. A fan is about £30.
Stoves Customer Care Number- 0871 222 2502
Lines are open Monday to Friday 8am - 6pm, Saturday 8.30am - 2pm, and Sunday 10am - 2pm.
Stephen Ives, December 2007