Flour Question, Please help!

My husband wants a Red Velvet cake for his birthday, so I've looked up a recipe. It calls for 3 and 1/2 cups of cake flour. So should I use plain flour or pastry flour. Also, should I increase the amount of flour for the recipe. I read on a website that UK flours are more moist than American flours. I think I saw on here that you should add 1/4 cup to every cup in the recipe to work it out. Any suggestions will be greatly appreciated.

I would use plain flour.  Cake flour in the US has lower gluten content, UK plain flour has less gluten than US A-P flour, but I'm not sure how much less.

Usually people here add extra flour because the UK flour won't absorb as much fat. 

Maybe you could make a test cake?

Why not just use a British recipe so you don't have to bother with substitutions?

I would think, since your recipe is already calling for a low-gluten flour that you shouldn't need to add any extra flour.  If you see what I mean.