Spy Action Library #1 is a digest-sized Yaffa comic published c.1974:
The Fanatics was also published by Yaffa in Spy Stories Picture Library #3:
Again, as was often the case, Chatto was tasked with supplying a cover image for recycled material for which he had already provided a cover. There is no similar panel in the comic to suggest he swiped/tailored it for his purposes.
I say he had already supplied a cover, but I'm not sure of the publication sequence of these issues. I can usually tell which edition was published first by the cover price. In this instance each edition has a $0.30 cover price, leaving me to make deductions. Common sense dictates that Spy Action Library #1 was first out the gate, given the cover is based on the source material.
However, I note that Spy Stories Picture Library #1 was published with a $0.25 cover price, and ran for at least 4 issues, whereas I'm not sure there were any further issues of Spy Action Library. So it is possible Spy Stories Picture Library was considered the primary series, and Spy Action Library was an afterthought.
I also note there is a 7 marked in pen on my copy of Spy Stories Picture Library #3, indicating a publication date around April/May 1974. AusReprints has an indicative date of December 1974 for Spy Action Library #1, based on the advertiser's code MMBO/1274. The code on Spy Stories Picture Library #1 is MPHO/1274. Should I accept that they were both published simultaneously? It's possible, I guess, but it doesn't scan with the April/May date ascribed to Spy Stories Picture Library #3.
I must admit I tend to be a bit frustrated and sceptical about the accuracy of the date codes on Yaffa comics. I think they're useful for indicating a year, but less accurate regarding the month of publication. My impression is that they tend to be too generic or 'long term' compared to the date codes on K.G. Murray Comics. I may change my mind about this as I become more familiar with the early/mid-'70's Yaffa catalogue. I don't yet have a handle on this period as I do on Yaffa's Marvel period.
Oh, and I look forward to spotting another issue recycling the Fanatics!