To wrap this up - this was bugging me so much I booked in for a retest in a different centre. And guess what, perfect, passed without even an advisory.
I didn't do a damn thing in the meantime, so I do think they messed up the first time. Anyway, 40 quid extra for a retest, a good end result, and learned something knew about awd and the NCT.
I did make sure to stress it was awd handing in the keys so who knows whether that was it or the first place just didn't do the test right. guess I'll just make sure to always tell them that in future for peace of mind. (oh and Gordon - yer bang on, I was watching like a hawk and as you said, front wheels no movement, back wheels moved in opposite direction to each other)