Pleased to say I sorted this out. I set up my mount (SXD2) with an approximate PA, using compass and altitude, and start tracking (not using AsiAirPro, but Starbook 10)
I then do an all sky PA using AAP, manually rotating the RA axis for the plate solves using the SXD2 slew buttons.
PA adjustments quickly result in a fairly accurate PA
I then reset and do it a second time and it gives consistent results within a few arc minutes, guiding is OK