This is what the BR network could have looked like, by the 1980s, had the Beeching II developments gone ahead. All lines except those shown in bold would have been closed. Swathes of the country — notably North, South West Scotland and most of Wales — would no longer have lines. The plans were quietly shelved and closures slowed. Beeching resigned. 
Notes:

Some suburban lines around certain cities (e.g. London, Birmingham, Glasgow, Manchester) would have been kept open for commuters; this is not acknowledged on the map.
The Woodhead route (Manchester to Sheffield) is shown to be kept open on this map, but was axed in the 1980s.
The faint lines are examples of major through routes that would have closed. Most of these remain open to this day, although some were axed subsequently. Of these, some have re-opened or are planned to re-open.
self-made, based on an a poster from Beeching II report
Was done on behalf of the Wikipedia User:Btline (original image up-loader) by Cronholm144 via the Wikipedia Graphic Lab