Some more work done tonight:
Soldered up the second of the three boards so that it can run off the bike's 12v supply (Fused Ignition feed):
This means no worrying about charging batteries and no need to press the on button to start it up.
Also it fits into a smaller box than combining the battery and board:
So a few small bits need to arrive and then I can fit it to my bike and go ride.
Out of interest which voltage source would any of you prefer if you had a need for such a device?
1) Battery only (Easy to move around the bike for different shots)
2) Bike's battery (No need to worry about charging batteries)
3) Both please!