Why does my red velvet cake not turn out correctly when I make it in the UK?

It calls for eggs, sugar, self-raising flour, vegetable oil, baking soda (I even bought Arm & Hammer from the US to see if that made any difference), cultured ermilk, red food colouring, and vanilla. Are there vast differences to the composition of these ingredients here in the UK vs. the US that could make the batter gummy and the cake not rise properly?