Place the butter and milk into a small saucepan and heat on low until the cubes of butter are completely melted. Set to one side to allow the mixture to cool for a few minutes.
Place the flour into a large bowl and add the yeast to one side of the bowl and the salt and sugar to the other. Roughly chop the raisins and mixed peel, then add the dried fruit to the bowl.
Beat 1 of the eggs into the lukewarm milk mixture. Gradually add this into the dry mixture, stirring all the time, until a sticky dough forms.
Turn the dough out onto a lightly oiled surface and knead for about 15 minutes or until it is no longer sticky and it has become a smooth and elastic dough. Use a dough scraper if you wish. Place the dough into a lightly oiled bowl, cover with clingfilm and leave in a warm place for 1½-2 hours or until doubled in size. While the dough is rising, mix together the cinnamon, mixed spice and caster sugar in a small bowl.
When the dough has risen, turn it out onto a lightly oiled surface and fold it in on itself a couple of times to knock out any large air bubbles. Roll the dough out into a large rectangle, about 45x30cm, and spread the soft butter over the top using your hands. Sprinkle the sugar and spice mix over the dough and press it into the butter. Roll up the rectangle, starting at the long side, and then slice into 12 rolls.
Arrange the rolls on a large heavy baking tray lined with baking parchment (or 2 lined baking trays), cover with oiled clingfilm and leave to rise for a further 30-40 minutes until noticeably larger. Preheat the oven to 200°C, gas mark 6.