Preheat the oven to fan 200`c. Wrap a bacon rashers around each sausage then put them, spaced apart, in a large roasting tin (preferably metal). Scatter over the onion and drizzle with oil. Bake for 15-20 minutes until the bacon and sausages are starting to colour and the onion is tinged brown at the edges. Meanwhile, make the batter. Sift the flour and a make a well in the centre and crack in the eggs. Beat lightly and then gradually pour in half the milk and water, beating all the time to form a smooth, thick batter. Continue to whisk for 2 minutes before stirring in the remaining liquid, chopped rosemary and season well with salt and pepper. Remove the sausages from the oven and quickly pour over the batter. Return back to the oven and cook for a further 35-40 minutes until the batter is crisp and well risen. Meanwhile, make the caramelized onion gravy. Heat the butter in a saucepan and soften the sliced onions together with the thyme for 3 minutes. Add the red wine and cook down for 20 minutes to intensify the flavours. Next, add in the hot water, beef gravy pot and season well with black pepper. Stir well and continue to cook for just 3-4 more minutes to obtain a delicous, rich gravy. Serve the hot toad in the hole drizzled with the red wine and caramelized onion gravy.