What is the difference between self raising flour and wholemeal self raising flour?

I'm assuming you mean whole grain wheat. Whole grain wheat includes the bran, the germ, as well as the "flour" part of the berry. It is much more nutritious.

Self-rising flour is make from white flour, which is wheat that has had the bran and germ removed. This pretty much leaves dead cellulose, which they then add some chemical vitamins to, and call it "enriched". Then they add some baking powder (often-times, with aluminum in it) and call it "self-rising" flour.

Better to add your own non-aluminum baking powder to your flour.