I was at Highgate School from the late 40's to the late 50's and used Hampstead Heath quite a bit from time to time. Memory is a bit rusty but perhaps a bit of oiling would help! Not quite sure what you are looking for but if that period could be of any help, let me know,
Don't know if this will help, but there were/are 3 pubs at the heath.
Jack Straw's Castle.
The Old Bull & Bush.
The Spaniards Inn.