I make this cake as stress-relief for my exams (what with you geting to mash it together with your hands!) and I can guarantee that every time you make it it'll come out moist and (close-enough) perfect! I usually sandwich it with jam and chocolate butercream, but for a summer party you can't beat halved strawberries and whipped cream.
Make sure you sieve EVERYTHING that can be sieved- that's what makes cakes light and spongy.
The baking powder with the self raising flour may seem a bit excessive, but I always use it to get enormous cakes and as an insurance policy against poor quality flour or (as happened to me once) plain flour getting put into the s/r flour box.
Very Very tasty Highly recommended - 30 Oct 2010