Hi Alanlad
Here's a very easy recipe to follow:-
http://www.tarladalal.com/recipe.asp?id=107
It is absolutely vital that the eggs and sugar are beaten really well and that the flour is very carefully folded into the mixture. Too heavy a hand on the folding will mean that air is lost from the mix and the sponge will be heavy. Another tip is to ensure that the eggs you use are at room temperature if you normally store them in the fridge. I suspect that *tea sugar* is caster sugar btw.