My research on his early work has drawn out some interesting early examples of ideas he reuses in later work. This episode from 'Roscoe Moscow' (dated November 3rd, 1979) is really interesting:
Look at the opening speech balloon, particularly this line - "They say there's a broken light for every heart on broadway". I knew I'd heard or seen that somewhere before, and then I realised that it's
the opening line in 'This Vicous Cabaret' from V for Vendetta (Warrior #12, August 1983):
The audio version can be heard here
I was also sure I recognised Captain Billy's Bar from somewhere, and I was right. Moore uses the name in his and Don Simpson's In Pictopia (Anything Goes #2, December 1986):
Finally, I found that the name of Rocket Redglare, and the concept of the aging hero, were both later reused in a 'Future Shock' story from 2000 AD, 'The Regrettable Ruse of Rocket Redglare' (2000 AD #234, October 1981).
I wonder if I'll find any more similar examples as my research continues?