Really, the easiest solution that requires minimal wiring and messing about is to buy the 'Slice of Pod' from WirelessThings when you buy the ARF.
https://www.wirelessthings.net/slice-of-pod-raspberry-pi-to-i-o-pod-plug-and-play-boardIt looks like this.... and the second photo as is when fitted.
I believe a couple of other builders have used it since I posted my original picture - has a 3.3v reg on board and good indication on the board as to which pads to use - you only need to solder 4 wires. It is also cheap at just over £3
The other Pod and the Digole board require glueing into the case - this is just plugged in and can be removed easily.
Only thing required to 'modify' is the removal of the two 'pod' headers which can be 'wiggled' side to side and they will just break off - they are a bit of a bugger to desolder as the board uses plated-through holes.
