The Pertwee era was a big influence on the NAs, even though it was the height of the anti-Pertwee movement. Frontier in Space was also influential, and I've seen it pointed out that the NA's theory of time travel is deeply indebted to The Time Monster (chronovores, the time vortex, interstitial time etc.). The Mutants is another influence on stories like Original Sin. Maybe because the Pertwee era had an internally-consistent future history, and one fitting the kind of pessimistic futures that moody, politically progressive NA authors wanted to write!