*2 tablespoons of carbonated water, not sodium bicarbonate PER 100g of flour. Don't add 2 TBS of sodium bicarbonate per 100g self raising flour otherwise you're going to have a inedible bun/cake :)
yelenots: Are you using a gas oven, electric oven or fan assisted oven? You may not have the temperature right. Too high and they won't rise before you have to take them out. Too low and they will burn and be uncooked.
yele, try using a recipe for 'angel fan's which has a very light texture. Not sure how results will be for cupcakes, but give it a try. Just follow the part of the recipe for the cake, then decorate how you would normally. http://www.bbc.co.uk/food/recipes/angel_food_cake_with_04002