How can I get rid of the low disk space notification?
Right, I have the solution. Swipe down to get notifications, then hold down on the screen where it says 'insufficient storage'. A little window will appear saying 'app info'. Press that and it will take you to settings of your android system. There is a ticked box saying 'show notifications'
Untick that box and the problem is solved.
( the box can be ticked again afterwards, so you can receive other notifications, but the problem should not reoccur).
(as of 2020, you can no longer uncheck that box)