I don't add milk either. I use 2/3 eggs. You can weigh the eggs then add the same weight of marg (I use Stork), sugar (caster) and SR flour.
I cream together the marg and sugar until the mix is more white than yellow. Then add eggs a bit at a time, with a bit of the flour if it looks like it may curdle. Then fold in rest of the sifted flour, in a couple of stages, not all at once.
I use 2 sandwich tins.
I have oven at about 180C and it is a fan. I look at it at about 20mins ish and then decide if it needs longer- until springs back when gently pressed, as Jo says.