I wouldn't have cut anything, however there are a few lines which I am surprised remained open given the mood of the times: for example the Uckfield line, or Eridge-Tunbridge Wells (which did close, but not until 1985) or the Elmers End-Sanderstead link (again closed later). Also Dorking-Horsham (sending all trains through Gatwick as actually happened later).
Note, to be absolutely clear, that I would *NOT* have wanted any of these lines to close, particularly Uckfield and Dorking-Horsham, but surprised, given how savage the cuts were elsewhere, that these lines, which mostly traversed rural areas which must have been sparsely populated in the 60s, were not closed at the time.
I am particularly surprised Eridge-Tunbridge Wells lasted so long, as it didn't provide a useful link to anywhere (other than Crowborough and Uckfield to Kent, which can't have been a huge market) once the old route on to Lewes was truncated at Uckfield. If they kept that open, why not Uckfield to Lewes? Then there could have been genuinely useful through services from Brighton to Kent. Seems strange to close one and not the other, would have been more sensible to keep both (my preferred option), or close both.