Why Mark 37 directors arrived too late for most wartime ships

Did the Royal Navy use American Mark 37 anti-aircraft directors during the war?

Only in small numbers; most were allocated to late ships such as the Battle class and Vanguard that reached service at or after the war's end.

Mark 37 directors were available to Britain and were intended for several new classes. The principal recipients mentioned are Battle-class destroyers and HMS Vanguard. Those construction programs matured so late that few systems became operational before the fighting stopped. The limitation was therefore delivery and ship-entry timing, not a total absence of the equipment from British plans.