Wednesday 26 November 2014 9.18pm
I'm no mechanic, but have riden motorcycles since the 70s.
It could be one of three issues that are plaguing your Ninja:
Battery, Starter, or sparks.
Whatever one of these is a problem, it is always good practice to take your MC for a winter service when the cold season approaches: not a full factory service, but just a basic once over.
New plugs, basic lube job, full oil change, new brake fluid etc.
When I was riding, I used the garage in Great Suffolk Street
that was used by many Dispatch Riders (always a sign of good honest work).
However I don't know if they are still there or not.
Best wishes and happy biking!