I know of at least two season one episodes of Space : 1999 that heavily use classical music....
Space Brain (Moonbase Alpha gets covered in foam -
foam party!) - this used 'Mars' from Holst's 'The Planets'
Dragons Domain (A veteran space pilot revisits a graveyard of ships, and its alien inhabitant) - 'Adagio in G Minor' by Albinoni
It's true that the stylistic differences between the two seasons do carry over into the music. Season one was scored by long time associate of Gerry Anderson - Barry Gray (Gray also scored Thunderbirds, Captain Scarlet, UFO, Stingray and more...) - the more orchestral of the two seasons, yet reflecting music of the period. The second season was scored by Derek Wadsworth - more uptempo, and sometimes 'far out'!
All the best,
Ian W359
