Hi Dave,
Performace power tools are made exclusively for B&Q, there are no spare parts avaliable to repair these machines, as for your saw, I think if you have a close look at it, the fault will lie with both the drive end of the armature, and the drive cog, both of which would have to be replaced as a pair - if you can find any good second hand ones!!
I hope this helps.
Dave the tool repairer, June 2007