How to change carbon brushes on Vax Rapide XL carpet washer?

Anybody out there with the knowledge to tell me whether the carbon brushes can be changed on a Vax Rapide XL carpet washer, how to do it if they can and where to buy a new set would be good as I seem to be struggling to find new replacements. Wife borrowed the cleaner from a friend and would hate to give it back in current unusable state so any info received would be greatly appreciated'
Many Thanks