Sharon - I use much the same recipe, but I use dripping (being a Yorkshire lass) and I rest my batter in the fridge for at least 4 hours before cooking. I believe there is a scientific reason for doing so but that is how I was taught (before fridges it was the cellar steps). It works beautifully, but the dripping must be smoking hot when you add the batter and get it in the oven. Terrific for toad-in-the-hole.
My mother taught me that the secret to perfect yorkshires was smoking hot fat. She also used to make the batter the night before and leave it in the fridge until the next day, I forget the reason for it.