Pencils and inks credits from Nick Caputo via the GCD Error List (15 March 2007).
All references to anything "Soviet", "Communist" or "Red" are amended throughout this story (as they generally are in Marvel UK's reprints); examples are "jet" for "MiG", "to the homeland" for "behind the Iron Curtain", "ya creeps" for "comrades", "the Hulk's foes" for "the wily Reds" and "would-be conquerers" (sic) for "Communists".
Between pages 7 and 8 of the Hulk story.
Page 12 introduces the second half of the story with a "new" splash page, which appears to be composed of diverse elements from elsewhere: there is an inset top right of Dr Octopus which is clearly by Ditko, a blurb in the bottom left corner ("Plus: a special guest appearance by the Human Torch!") which from its style is definitely from a previous US Marvel (splash page or cover), and between those two elements a full-page illustration of Spidey which is also by Ditko, not enlarged from within a story but perhaps taken from a splash page or pin-up.
The new splash page featuring the figure of Spider-Man is the pin-up page from The Amazing Spider-Man (Marvel, 1963 series) #3, with all the text elements replaced. The figure of Doctor Octopus is from the original issue, story Page 5, panel 3.
Between page 3 of the Spider-Man story and the letters page.
Between the Spider-Man's mask pin-up and page 4 of the Fantastic Four story.
Three colour panels from earlier issues (one each from Spider-Man, the Fantastic Four, and the Hulk) accompany the letters.
Letters from: Rory Calhoun (Dublin), John Williams (Fulham), Jerry Collins (Ramsgate), Rick Jones (Swansea) and Gaynor Davis (Cardiff).