Hotpoint Aquarius WD64 Will not spin properly?

My WD64 runs through the cycle correctly but doesn't spin - it starts to spin for a few seconds and then stops.
I have checked for any blockages - none found, it empties fine and the motor brushes were replaced about 6 months ago.
Any help / advice much appreciated.
We have 2 little children so you can appreciate it's important to get it sorted.
Many thanks