Fault finding and repair on a Miele S5211?

My wife owns a Miele S5211 Vacuum Cleaner and the power button will start the motor for a few seconds then stop. When the appliance is left switched on, it will start intermittently, then stop again.

I'm assuming that the foot switch is defective, and simply requires adjustment or even a replacement! I hope this isn't a dumb question, but how can I dismantle and gain access to the switch housing from the main body of the appliance?

I can't find any repair manuals for this particular model of vacuum cleaner, and I would be most appreciative if anyone can advise me of the correct proceedure.

Thank you in advance.