Ford UK like other carmakers in Britain were still recovering from the war for it to be practical, however though less then ideal they could have simply appropriated Ford of Germany's pre-war plans for 1.5-litre SV and even (933-)1498cc OHV versions of the easily tunable Ford Sidevalve engine (the latter later appearing in the OTL 1955 Ford Taunus P1 15M) for use in the post-war Anglia models from the pre-war bodied E04A / A54A up to the 100E.
But UK Ford already had the lines in production for the V8 Flathead at Dagenham, for powering the Bren Carriers and such. Makes more sense to use them, than to retool for another type for export sales.
They needed to sell something ASAP in 1946 for the US market, as Henry Ford II had decided before the War ended that Ford wouldn't do a smaller model. Don't want to wait for the Pilot to be launched.
Ford USA had already found that there wasn't a market for the 4 cylinder anymore in 1935, and Crosley would find after the war.
The only inline four that really kept sales in the US was the Willys Jeep