Hangarshuffle (your #19),
Indeed I did (my long and weary tale is told on "Gaining an RAF Pilots Brevet....." from Page 114, #2262 on).
Of course things were different in '41, Hitler's and Mussolini's "Flagged Vessels" were bottled up by the Navy; the rest of the world carried on sending us food, fuel and raw materials as usual (admittedly most of it was carried in British-registered ships). The US, our Dominions and pretty well everybody else were "on our side".
But all that counted for nothing if the ships went down: then as now this country can't feed itself: the Navy did a grand job but in '41 the Battle of the Atlantic was a losing battle until Bletchley Park turned the tables and (I believe) could provide the Admiralty with the daily position reports which every U-boat had to send back to base. This enormously simplified the task of finding them, and enabled us to route the convoys around their "wolf packs".
IMHO, the next WW will be non-nuclear (because of MAD - unless we are mad enough to get rid of Trident) and we may be in a like situation again.
Merry Christmas !
Danny.