Thanks John, I've been out and done it now so hopefully all will be well tomorrow, I appreciate your help.
Thinking back it did fall out of the back of the car when i was untangling the hose, so that may well be it.
I cant complain, had it a good few years and use it for all my upstairs windows, must have earned me thousands.
Been quite a saga really, bought new charger, then new battery, cheap voltmeter before working out it must be the pump, feel a right berk!
Thanks mate.