There are hints in the first few panels of the story that the spacewalk seen is being staged on a movie set: panels 1 and 3 have partial lines drawn in to represent the wires holding the actors in "space" (possibly a subtle comment on the occasionally visible wires on spacewalkers and ships in the actual UFO TV series!); the alien craft in panel 2 does not exactly match the UFOs used by the aliens being fought by SHADO; the alien in panel 4 looks a bit non-human and his spacesuit does not match those seen in the series.

In the later panels of page 1, it is seen that the "alien" spacesuit worn by actor Buzz Peters does have some similarities to the spacesuits of the actual UFO pilots.

Buzz thinks his alien make-up is crummy and asks if he can't have three eyes or four arms or even a green face. Ironically, the real aliens do have green faces due to the green-liquid environment of their spacesuits!

Most likely the name "Buzz" for the actor playing the alien astronaut in the movie was named by the author for real world U.S. astronaut, and second man to walk on the Moon, Buzz Aldrin.

The alien pilot hijacks a car on Highway 14, about 40 miles from Los Angeles. This is an actual highway, called State Route 14, which runs through the southern California desert from approximately Los Angeles to Highway 395 near Inyokern in the Mojave Desert.

The car hijacked by the alien appears to be a Plymouth Barracuda of the 1967-69 body style. On the last panel of page 2 of the story, the cursive Barracuda emblem can just barely be made out, though it would not be legible if one did not already know what it said.

Page 3, panel 4 of the story implies that Colonel Foster was already in Los Angeles, at a secret SHADO base there, when the UFO shenanigans in the southern California desert went down. 

The police car that intercepts the Barracuda-driving alien on the studio lot looks similar to the one seen in Britain that chases Straker in "The New Boss". And the one here looks even more like a DeLorean than the one in that previous story...still several years before the DeLorean was designed!
Police car	DeLorean DMC-12 (from mad4wheels.com)

The towering land formation in the background of page 4, panel 9 of the story looks more like something from Utah's Monument Valley than the relatively unspectacular landscape of the southern California desert.

Page 4 of the story reveals the L.A. film studio depicted to be called Futura Film Studios. This appears to be a fictional film company.