Richard remembers Gabby hanging out of the first floor door of the Stores pulling on the rope which held the instrument whilst us "youngsters" steadied it from below.Richard, Alan and I reckon the following names:-
From foreground to background on the left are Richard (cap), Gabby with his usual scarf, Gerry Chapple, possibly Norman Trinkle and finally me (Willy), in cap/glasses at the back.

From foreground to background on the right are Roy, Richard's dad (Mr. Curtis), and Peter Trinkle standing on the trolley beside the piano, We don't know who owns the knees.

Can anyone else help with names please?

Yes I know it's unnecessary calling Richard's dad Mr. Curtis but naming names helps the search engine database. - Willy