In a large bowl sieve the flour, salt and mixed spice. Then rub in the butter using your fingertips until the mixture is the texture of fine breadcrumbs. Stir in the sugar, lemon zest and yeast.
Beat the egg with the warm milk then add to the dry ingredients. Mix together to a form a soft, pliable dough.
Turn out the dough onto a lightly floured work surface. Sprinkle over the mixed dried fruit then knead the dough lightly for about 5 minutes. The dough should be smooth and elastic with dried fruit throughout.
Grease a large bowl with oil. Shape the dough into a ball and place it into the prepared bowl. Cover with cling wrap and set aside in a warm place for 60 - 90 minutes to proof. The dough should double in size.
Turn out the proofed dough onto a lightly floured work surface and divide it into 12 equal pieces, roughly 3 ½ oz each. Roll each piece into a ball.
Grease a baking tray with butter and transfer the buns to the tray in rows 4 x 3. Cover with cling wrap and return to a warm spot to proof for another hour, until the rolls proof together.
After the second proof preheat the oven to 400°F (200°C). Brush the buns with egg wash for a shiny finish.
Bake for about 20 minutes, or until golden-brown.
As soon as you remove the buns from the oven, brush them with a little warmed honey or golden syrup then set aside to cool on a wire rack.
Whisk together the icing ingredients until smooth but stiff enough to hold its shape. If it is too stiff add a splash more milk.
Scoop into a piping bag fitted with a small nozzle. Carefully pipe a cross on the cooled buns. Set aside while the icing sets for 30 minutes.
Serve the buns with butter and a big cup of tea. Store leftovers in an airtight container at room temperature for up to 2 days.