Remove sausages from their casings and cook them in a large frying pan over medium heat for about 5 minutes, then add diced chorizo and cook while stirring for a couple of minutes. Remove to a large bowl and set aside.
To the same frying pan add chopped onion, red bell pepper and cook over low heat for 5 minutes, then add mushrooms, a pinch of salt and Spanish paprika and continue cooking until mushrooms are done and the liquid has evaporated, then add minced garlic clove and cook for 20-30 seconds. Combine with the cooked sausages and chorizo.
In a separate large bowl combine the eggs, milk, dijon mustard, Worcestershire sauce, salt and Spanish paprika, whisk until well blended. To the bowl with the meat and vegetables, add the the cubed brioche, green onions, parsley and both cheeses and gently mix everything together. Then transfer the mixture into a buttered 13X9 inch casserole dish and pour the egg mixture over it. Cover with aluminium foil and refrigerate overnight.
In the morning preheat the oven to 180C/350F and bake the breakfast casserole uncovered for 50-60 minutes until puffed up all over and the center is no longer wet.
Notes
Alternatively you can bake this casserole immediately if desired.