I would put 1969 as the "departure date" there was an awful lot of re-releases back then, as the US turned away from Stax/Atlantic & Motownesque to protest tunes. I remember pouring over a UK releases book at our local record store and ordering stuff, I now realise they were not the original mid sixties issues. I would love to start/have a list of original UK releases and their subsequent re-release before Mojo & Contempo stuff. NS didn't happen overnight, it was a ground swell, all that I know tells me its origins can be dated to 1969.
Chris
ps : the Contempo release of Johnny Williams plays a damn sight better than that hissy Bashie..............