I have made these so many times and they always go down well with family & friends, so here is the recipe below.
For the base
125g butter or margarine, softened, plus extra for greasing
50g caster sugar
175g self-raising flour, sifted
For the filling
200g condensed milk
125g butter or margarine
125g caster sugar
2 tbsp golden syrup
175g milk or plain chocolate, broken into small chunks.