If ya ain't got fat from meat, ya canna make tha gravy. I'd say we could donate gravy, chickens, and maybe beef to the poor Brits, but like the guns we gave in ww2, they'd probably just give them up and go vegan while only a handful of better off individuals held onto some of their meat and gravy, but the automatic egg layers would have to be turned in, while only single shot or impotent roosters would be allowed to be kept and cooked You could still make as much gravy as you want, but the flour has to be kept in special cabinets when not being cooked with.
BS you can make gravy using boullion, water & roux (flour & oil)
But the best gravy comes from animal fat - pan drippings to make the roux instead of oil. And I like corn starch as a thickening agent more than flour, as it does not burn as easy as wheat flour.