Whisk together flour, sugar, spices and lemon zest in a large bowl.
Add the salt and yeast to the bowl, placing them on opposite sides.
Add the melted butter and half the warmed milk to the dry ingredients. Stir until a dough starts to form.
Gradually add the remaining milk, stirring until a soft, pliable dough forms. You may not need to add all of the milk.
Turn the dough out onto a lightly floured surface. Begin kneading the dough, incorporating the sultanas and mixed peel as you go. Keep kneading until the dough forms a smooth, silky, and elastic ball (about 10 minutes).
Place the ball of dough in a lightly greased bowl. Cover the bowl with a piece of plastic wrap and leave in a warm place until the dough has doubled in size (about 1 1/2 hours).
Turn the dough out onto a lightly floured surface. Divide the dough into 12 equal sized balls. Place on a parchment lined baking tray about 1 1/2 inches apart.
Cover with plastic wrap again and leave for another 40-60 minutes until the dough balls have doubled in size.
Pre-heat your oven to 425°F and then start on the topping. Mix together the flour and water to form a paste. Transfer the paste to a small piping bag and pipe a cross onto the top of each bun.
Bake for 15-20 minutes until golden brown.
While the buns are still warm from the oven, brush with some melted golden syrup, marmalade or apricot jam, to give the buns a shiny finish. Transfer the buns to a wire rack to cool completely.