I think that Volume Three was the first one I bought, at the end of 1969, rapidly followed by Volume 1 (it might have been the other way around). When Volume 4 came out I had the vast majority of the tracks on single and so gave it a miss .... the same was the case with all future volumes, though I did get a second-hand copy of Volume 2 at some time in the early '70s.
When they came out on CD I bought a copy of all of them, in Woolworth's in Barking if I remember correctly.
Roger