Cut the bacon small and keep it on top of the cheese, not under it. Small pieces crisp in the time the bread takes; a whole rasher, or thick cut bacon, will not. If you want it crisper, fry it for a couple of minutes before it goes on.
Judge it by the eggs, not the clock. The whites want to be opaque all over with the yolks still soft. Whites set at about 65C but firm up hard by 80C, so a couple of extra minutes is the difference between tender and rubbery. They keep setting out of the oven.
Self-raising flour instead? Use it and leave the baking powder out. Self-raising is plain flour with baking powder already in it, about the same amount the recipe adds. Both together and it rises fast, sinks in the middle and tastes soapy.
Crack the eggs on first, straight onto the flat batter, before the sausage and tomato go on. Onto lumpy toppings the whites run down the sides and set unevenly.
The hob minute matters if you are using cast iron - it sets the base from underneath and is most of the reason this bakes in a quarter of an hour. Skip it for a thin cake tin, which will scorch on a burner.