Hi there,
Unfortunatley the Brayford is one model I haven't dealt with, but I have repaired very similar models. Obviously it's difficult to give specific instructions but it's usually just a case of removing the screws securing the back of the stove to give access to the small motor which turns the flame effect rotisserie. The motors are actually very easy to change - usually only being secured by two screws and two pull off electrical connections. The flame rotisserie is usually attatched to the motor shaft by a rubber coupling which simply pulls off.
This company is very helpful and reliable for spare parts.
http://www.electricspares.com/acatalog/Online_Catalogue_Optiflame_Fires_3.html
They don't list your model but they may be able to get the part for you as the same motors tend to be used on several different models.
Hope you get sorted out OK.
Regards,
Lee
Lee, April 2008