Samsung Galaxy S2 i9100 erratic battery status

I really like my S2, but the last week or so I've noticed an annoying problem with some bizarre symptoms. At first it looked firmware related, but as investigated further pointed more towards hardware. Either battery, the sensors within the battery or the micro USB charging port.
Symptoms;

• when switched off and without a USB lead connected the phone display alternates between a battery level indicator (as if charging) and a temperature warning.
  Plug a USB lead in to get past this and boot the phone normally
• When switched on and you've received a 100% charged notification, rebooting the phone and checking the battery level again, shows the battery hasn't charged to 100%.
  I'm trying to force mine up to 100% by rebooting every time it stops charging to charge it a bit more. This might get it over the hurdle eventually...
• With no lead plugged in, trying to disable USB debugging mode (settings>applications>development) gives the error: "USB  is connected. Remove the cable"
  I've got no fix for this yet, except maybe flashing a clean ROM onto the device with the debugging mode already disabled

There are a few forums dotted around that describe this and offer a couple of solutions that seem to point to the problem being the micro USB port itself; the solutions I have found are;

• Clean the micro USB port- switch the phone off & remove the battery. using some isopropyl alcohol, some cleaning tissue and a toothpick, carefully wipe the 'tongue' of the port, the side nearest the screen primarily  Gently tease the tongue up towards the screen also. This assists the lead make contact properly
• Contact a Samsung service centre, giving the details of the problem and that it has reported as a problem globally. As the symptoms can be erratic, they may not see the problem at first, but a skilled engineer should be able to replace the USB port in under an hour (according to reports)
• Replace the USB port yourself. The part can be found at http://www.tvc-mall.com/details/Samsung-I9100-Galaxy-S-2-Dock-Connector-Charging-Port-Flex-Cable-Ribbon-Original-SAMF-I9100/ and detailed disassembly instructions are also floating around.

I don't advise the last option as it will most certainly invalidate any warranty you may have.