Hi John,
Performance Power tools are made exclusively for B&Q, and there are no spare parts available for these, however in saying this, most of the imported machines use the same parts, as the company who makes them (GMC)make machines for a lot of different companies.
The easiest thing for you to do would be to take out 1 of the brushes from your saw, and take it to your local power tool repair shop, or local hire company, and ask if they can match it up with something from a 'branded' machine, as there is a 99% chance that it will be the same as, or similar to a Makita or Hitachi brush size, you may have to sand the brush to fit, but this is easy to do, as the carbon is soft.
The Applegate internet directory is always a good place to look for your local power tool repair shop, if you don't know where your local shop is.
I hope this helps.
Dave the tool repairer
August 2007