I switched my phone off and then on again, whilst still not plugged in ...after switching back on, the charge bar has at least stopped moving up and down, and is now more than 3/4 full now, which is probably about right.

Ill await the next update to see if it makes a difference, although the power light can flicker slightly when moving the cable whilst charging (as a test).

I still believe the problem only started after I updated. The mini-USB connection does not seem to be damaged or loose in any way either. thanks