Start by cutting the rind off the bacon. Next, wrap one piece of bacon around the center of each sausage. Heat a frying pan and quickly brown the bacon wrapped sausages all over. Place the sausages in the oven proof dish while you make the batter. Place the flour into a bowl, and break in the eggs. Season well with salt and pepper, add the chopped rosemary, wholegrain mustard and mix together using a balloon whisk. Gradually add in the milk and water till you have a smooth batter. Pour this batter around the sausages in the dish, and cook in a hot oven for 30 minutes, at 220`c till golden brown. While the toad in the hole is cooking you can prepare the red onion gravy. Heat the olive oil in a pan, and add the sliced red onion and soft brown sugar. Cook the onions on a low heat for about 12 minutes until they are golden brown and caramelized. Mix the hot water and beef stock cube together in a measuring jug till the cube has dissolved. Add the red wine and Worchester sauce, and pour the liquid into the pan with the caramelized onion. Season well with pepper and salt, and stir the gravy well. On a low heat, continue to cook the gravy, for about 5 minutes. Mix continuously with a whisk till the gravy is thick and glossy. Serve the rosemary and mustard toad in the hole immediately as it comes out of the oven, with the delicious red onion gravy on the side.