Begin by zesting the orange, lemon, and limes, then set the zest aside.
In a mixing bowl, combine the sultanas, wholemeal flour, plain flour, oatmeal, rolled oats, bicarb, and a pinch of salt.
Add the cold, cubed butter to the dry mixture and mix until it resembles a crumbly texture.
Incorporate the unrefined caster sugar and the beaten egg, stirring until the mixture is well combined.
Shape the dough into biscuits and arrange them on a baking tray.
Bake in a preheated oven at 160C until they turn golden brown.
