Prick your potatoes all over and lay on the bars of your oven. Bake for 1 hour. Remove and leave to cool.
Heat the olive oil over medium-high heat and add your sausages. Fry for 5 or so minutes, breaking up the meat from time to time, until you have nice colour and it's a bit crisp. Turn the heat down to medium-low. Add your flour, stir through the oil/sausage until it's homogenous. Cook it for 30 seconds. Add your milk in 2 or 3 stages, stirring well to avoid lumps prior to each addition. Add mustard, salt and pepper and cook until the consistency of thick double cream. Remove from the heat.
Cut the top and bottom off your potatoes (so it can stand up). Cut a hole in your potato and fill with a bit of the sausage gravy. Go in with a little lump of cheese. Fill the hole with more sausage. Using toothpicks, pin 2 rashers of bacon to the potatoes so they're well covered.
Place on a lined baking tray and bake for 30-40 minutes at 180°C, or until nicely coloured. Bring out, glaze with barbecue sauce and pop back in the oven for 10 minutes at the same temperature. Bring out, top the potatoes with additional cheese and place back in the oven to make it erupt.