This was a very successful experiment because I didn't really have a recipe!
I greased and lined a loaf tin and put sponge mix in the bottom (200g marge, 200g sugar, 200g sr flour, 2 eggs) then put a layer of blackberries which I picked from the garden. Then I sprinkled crumble mix quite thickly on top. (I used 50g butter, 100g flour, sugar to taste.)
Bake at 180 degrees until sponge is cooked - about 45 minutes.