Rock buns are like a very rich scone to a certain extent, the ratio of fat to flour in a scone is usually 25%, in pastry it's 50% fat to flour. Rock buns are a bit of a cross between the two consistencies, 50% fat but with added sugar for sweetness, the addition of more liquid than you would use for pastry and it's milk with an egg unlike water for basic pastry. All this adds to the richness of the final result and the amount of sugar would be personal taste really, when you add dried fruit I feel you don't need as much sugar. Unlike scones they are not rolled out and shaped, more rustic looking but many places now make 'scones' from what is more correctly a rock bun recipe and you end up getting a very sweet, denser more calorific snack than a relatively harmless scone would have been!