The interceptors were only armed with one missle, SkyDiver had multiple missles available as each Sky had two pods on each wing and weapons mounted just front of the pilot cabin. Not sure about the Mobile units, if I recall right each one had its own particular weapons configuration.

The models in Space1999 were originally to be part of a second series of UFO, to be called UFO 1999 but that didn't happen and Space 1999 was created. So Eagles, and Hawks would have been the space hardware used against the alien craft.

Sure UFO has its flaws, as does the second season of Space 1999 but these series I loved as a kid and despite seeing those flaws more easily as an adult I still enjoy watching both series.