In reply to Tom Ripley Mountain Guide:
The listings in issues 1 and 2 of Mountain magazine - British Climbing since the war 1945-59 and 1960-68 - are useful sources here, as is Doug Scott's Big Wall Climbing:
Dru; both sources concur - Tom Bourdillon and Hamish Nicol, 26 July 1950.
Cima Grande; Mountain has Ian McNaught Davis and John Wilkinson in 1951, while Scott records their ascent as having been in 1953 following an earlier ascent by Vin Ridgeway (probably with Richard Meyer, and probably in 1952). No idea whether this has been resolved.
Badile; Alan Blackshaw, Geoff Sutton, Bob, Downes, Eric Langmuir, 1955 - reference Doug Scott.
There's general concurrence about the Walker (1959) and The Matterhorn (1961).