There's not much to cause a 13A fuse to blow - it's a 1200W motor which draws about 5 amps - I would guess a possible fault with the motor - a strand of loose wire in the plug - a bizarre wiring fault in the machine - or... a defective power cable... They get stretched and damaged with constant tugging over time.
If it were my machine I would first inspect the plug for loose wires - unless it's a moulded on plug which it probably is - then I would set it running on its own and not touch it for a few minutes - if it failed without being touched then i would suspect the motor.
If it ran OK without being tampered with then I would suspect the cable - Unplug and carefully inspect the cable for physical damage - if OK then set it running again and gently bend the power cord to see if the fault can be brought on.
Dysonmedic.com has good words and pictures about repairing these cleaners.
It might run OK on a 5A fuse but if it were mine I would fit a 10A or continue to use a 13A - whichever you have handy.
Good luck...
Peccavi
May 2010
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix vacuum cleaners.