On Sunday, 5 January 2020 23:12:16 UTC, Theo wrote:
I know this is DIY and all, but have you thought about just buying the
appropriate PSU:

(a) That's what I intended to do but through inattention (and not realising 5A and 5B were different power plugs) have already bought an inappropriate PSU
(b) the 5B PSU is rated at 2000mA which gives me an additional 500mA to play with on the USB port once I have bypassed the internal USB power supply and fitted an additional 12 to 5V thingmy.

Owain