Here's Keith Chatto's cover to Page Publications' Tales of Terror Picture Library #7:
This is based on a previous cover to Promise of Death. Here's a scan of the cover to Secret Service Club Library #41:
This issue was distributed in Australia with a $0.40 cover price. The GCD entry suggests this was a 1976 series. Both of these details place the publication date of Secret Service Club Library #41 well after Tales of Terror Picture Library #7. It does appear an earlier edition of this issue was published, possibly by Med Publishing, or another UK publisher.
It also appears this was the first Yaffa edition. I expect more will turn up.