Snow had variously Jeff Jones, David Brown, Bob Willis, Peter Lever, Geoff Arnold, Chris Old and quite a few others for fast bowling competition (I recall seeing Snow bowling a lot with Arnold a lot). Hall would have had Charlie Griffith as his main bowling partner, possibly also Watson and others I don't know; and Truman, Statham mainly, with appearances from Coldwell, Flavell, and Shackleton.
Snow's main competition for wickets in the second innings would have been Underwood and Boringworth, with Titmus around earlier too, and Gifford on occasion.
Hall would have been competing for wickets with Lance Gibbs, who is a former world record holder for wickets taken.
Trueman's spin competition would have been mainly Laker, Lock, Titmus and Allen.
Hadlee would have competed with Bracewell, Headley Howarth, straight-break Boock, and Deepak Patel, who are probably not in the same caliber as many of the others above, but who are probably not exceptionally poor when compared to spin bowlers in the late 70s and the 80s.