Preheat the oven to 180°C, 350°F, gas mark 4. Peel and slice the apples thinly, and put them in a bowl of cold water with a little lemon juice to stop them going brown. Melt the butter in a small saucepan over a low heat and keep warm. Carefully cut the filo pastry into 30x50cm sheets with a knife. Mix the pecans, cinnamon and dark muscovado sugar together. Lay the first sheet of filo pastry on a clean tea towel on your work surface and brush with melted butter. Sprinkle over 1/3 of the pecan mixture. Lay another sheet of filo pastry over the first one, sprinkle with pecans, cinnamon, and dark muscovadosugar, as before. Repeat with the third sheet and lay the fourth sheet over the top. Drain your apples well and toss with the caster sugar and dried cranberries. Spread them along the bottom edge of the pile of filo pastry sheets. Brush the top edge of the filo pastry sheets with a little water and gently lift the edge of the tea towel nearest you and use it to help you roll the pastry up lengthways like a Swiss roll, with t e apples at the centre and press together gently. Place on a baking tray and bake in the oven for about 20 minutes or until golden brown.