Hmmm how about RN sailors in uniform and wearing sandals (ref watching Sailor tv series and many other documentaries aboard RN warships) in Med and other hot areas? Sandals not exactly H & S, and never seen a USN sailor with open toe sandals and their uniform on decks let alone white shorts.
A sign of simpler times. Perhaps not H&S, but were certainly issue at the time. I still have my pair.
Sadly, a higher op tempo is now dictating a more utilitarian approach to dress. Most RN Ships now wear No 4 uniform all the time while at sea, only shifting into whites while alongside in aforementioned hot areas, and even then more likely to be long white trousers rather than shorts because of cultural sensibilities. I do believe, however, the final decision on rig is still with the CO of the Ship.