I've just cooked a two different fruit cakes and vanilla sponge. One fruit cake with 4 oz plain flour and 1.2 tsp baking powder instead of 4oz self raising flour. The other two as per recipe with self raising flour. All three seemed to have failed to rise. The flour was waitrose which has always been reliable in the past.
Firstly, what is the diference between using plain flour+baking powder and self raising. It seems i've got some 'duff' flour. I always thought one could use either in a recipe. It about five years since i did some baking so i'm trying to get back into practice but seem to have mislaid one of my recipe books which had alot of this info in it.