well a new battery was fitted on monday as the original one was dead. I charged it for a few hours after fitting it on monday just on the safe side even though honda said i didnt need to. After 6 days, on turn on the battery read 12.2v raising to 14.2v after start up.
I'll see how it goes over the next few weeks, I hope it was just the battery at fault.

Thanks for the update - I'm sure it's nothing else

I am a firm believer in fully charging a new battery on a decent charger at least once. Allowing for cold weather 12.2 volts is OK but only represents about 50% charge at most. If you can run for at least two hours on a continuous journey that will bring it up but failing that a modern type of charger will bring it up to 12.6 volts after standing and that more or less indicates full charge.

I've found that the voltage displayed on the screen when you turn on the ignition tends to read low, possibly due to the initial discharge when the lights come on etc. I left the bike for a week (in roughly zero degrees) and switched it on to see the display reading 11.8v but after switching off and then testing the battery directly, the meter read 12.5v, as you would expect.