With imports pretty much dried up, UK brewers were dependent on hops grown domestically and existing stocks. At the time, the majority of English-grown hops were Fuggles, Goldings or something similar. There was a bit of Brewer's Gold knocking about, but not a huge amount.
Brewers preferred the flavour of Goldings. But it was harder to grow than Fuggles.
"The author refers to the question of quantity and shows how it is still below brewers’ requirements. This shortage is likely to continue, and as it is doubtful whether American or Continental hops will be imported for some years to come, for they are short themselves, he is of opinion that at least another 3,000 acres should be planted. If permission should be given, what hops should be planted ? First of all there is the rivalry between Fuggles and Goldings. The Golding grower wants more money for his product because it is more expensive to grow, but one of the reasons given for this is that it is more liable to disease. It is true that the Golding is of higher flavour quality than the Fuggle, but is it really economical deliberately to grow a hop liable to disease for the sake of this comparatively slight difference in flavour. We say slight difference because we do not believe the general public can distinguish beers brewed with Fuggles from those brewed with Goldings, other things being equal. There are in fact quite a few brewers who, although well able to tell the difference between a Golding and a Fuggle whole hop, cannot tell their difference in the finished beer, especially in a chilled and filtered bottled beer. It is difficult to justify further growth of the Golding from the national economic point of view."
The Brewing Trade Review, March 1943, page 74.
Out with Goldings, in with Fuggles, then. I've no hard evidence that such a switch occurred. Very little evidence of any kind, unfortunately.
Just snippets from Barclay Perkins brewing records which, unusually, record the hop variety. 1943 - 1945, most of the hops they used were Fuggles, with occasionally Goldings, especially for dry hops. But the same was also the case in 1938, before the outbreak of war.