Our thanks to Christopher Clarke who has provided this picture.  
He dated it to 1955 (though possibly late 1954).

Back row, from left: 
[?], Elizabeth Bull, Jane Scripps, Maureen ?, Lesley Kennet, [?], [?], [?], [?], [?]. Andrew Puttick, Michael Sylvester
Middle row, from left: 
Kathy Polak, [?], [?], [?], ? Wilson,  [?], [?], [?], [?], [?], Ann Cornell, Anthony Flint
Front row, from left: 
[?], [?], [?], [?], [?], Mrs Scott [?], Robin Harding, Paul Beck, [?], Christopher Clarke