By 1979, Letraset's Action Transfers were being handled by Thomas Salter, whom they had acquired at the end of 1978 for one million pounds.
But when Letraset were themselves bought by Esselte in late 1981 (well after the trade catalogue shown below had been published), Thomas Salter were cut loose again, & so from then on their transfers were no longer branded 'Letraset' — as you'll see from the packets on the next page.

Scans courtesy of Ralph Rankin
"Four sheets containing 8 colour transfers — over 100 different HORROR pictures"
In other words, fifty (or more likely forty-eight) different sheets, with at least two transfers per sheet. At least, that was my original guess, but you'll see I was insufficiently generous in my estimate!

Scans courtesy of Ralph Rankin
These two scans were kindly provided by Ralph Rankin, & for a while they were the only sign of this particular series we've seen (but see below).
However, since all the artwork in these examples was also used previously in the GK175 Letraset Tattooze Multi-Coloured Skin Transfers from 1974, it's safe to assume we don't really need to see all of it to fully appreciate it!
I've now acquired a few more of these transfers, & discovered an interesting thing: the text 'Printed in Italy' prefers to remain stuck to the backing tissue, rather than the plastic. Presumably this is so that people don't rub it down by mistake. However, I've never seen this idea repeated, so perhaps it was a one-off experiment.

One of the great things about running this site is that occasionally someone comes up with the goods — in spades.
Jamie Holden sent in a huge number of scans — a huge amount of work — so, with thanks to Jamie…
Here: have fifty-one more sheets (well over one hundred more horrors)!

Scans courtesy of Jamie Holden
Despite the fact that this seems to be more than enough horrors, it's possible there may be more sheets because these sheets from the earlier GK175 Letraset Tattooze Multi-Coloured Skin Transfers series show a couple of horrors not shown above:

…Or possibly they simply didn't make the journey to the rub-down equivalent!

"Over 100 different monster transfers — Includes some special 'GLOW IN THE DARK' transfers"
As above, there were forty-eight, or possibly fifty, or possibly more sheets in total, with four sheets in each packet. We can give you a look at thirty-one & a half of them; I'm afraid ours won't glow, though!



Thanks to Elaine Jones for providing photos of the five transfer sheets immediately above.
The following are Tom Doyle's scans of this series, which previously appeared on StellarX' website, Seven Wonders. (Thanks for getting back in touch, Tom!)
Here are the Space Monster packets, as listed in the Thomas Salter 1981 trade catalogue:

See also: Combat Bubble Gum Instant Picture Sheets ↑
Plus: Topps 1969 Baseball Magic Rub-Offs ↑
And: Topps Speed Wheels ↑
And: A&BC Footballer Bubble Gum with Action Transfers ↑
Picture Credit: The SPLAT Scan Archives — Tom Doyle — Nic Comley — Elaine Jones — Nick Symes — Ralph Rankin — Adrian Allen — Jamie Holden