Pasta Carbonara a la TMR

This is my take on 'Pasta Carbonara', though it would be more accurately just called pasta with bacon and mushrooms in a cheddar bechamel sauce. More work than a traditional carbonara, but SO worth it. Personally, I don't use measurements so any given are rough estimates.
Serves 2-4 depending on how much pasta you usually eat in one sitting.
Flour: Plain/Self raising/whatever; I tend to use self raising since that's what I have to hand but it really doesn't matter. roughly 1 tablespoon.
Bacon: at least 1 rasher per person of back, or 2 of streaky, cut into chunky strips and fried.
Mushrooms: chestnut or standard white, chopped and sauteed in butter/the bacon fat.
Cheese: Cheddar, I use mature+ but strength to taste, 150-200g, chopped into 1cm cubes
Milk: Semi Skimmed+ (skim doesn't mix with the cheese as well) probably 200ml+, it varies every time but it can be boiled down later.
Butter: Real butter, that's basically the only stipulation.
Spices: English Mustard (the hot one, this doesn't add any heat but is essential), Paprika (unsmoked), pinch of cinnamon if you're feeling adventurous.

On a medium heat, melt 25g of butter in a saucepan and stir in the flour until it starts to fry; if it's lumpy/solid add a little more butter. This is a liquid rue so don't fully cook it out.
Slowly (splash by splash) add the milk, stirring until it's all absorbed before adding the next splash, and continue until you have a moderately runny liquid with no lumps (switching between on and off the heat can be useful here). Once you have about 1.5cm of runny lump free liquid, add the rest of the milk. Bring to temperature on a low-mid heat and add the cheese.
Stir constantly (figure of eight pattern prevents sticking)
Once the cheese has melted and caused the sauce to thicken up, stir in 1/4 teaspoon english mustard and 1/4-1/2 teaspoon (flat, not heaped) of paprika. The sauce should look cheddar-yellow (if you use red cheddar then this is not a good comparison, but that doesn't really exist in the UK afaik).
Add in your cooked mushrooms and bacon, allow a few minutes for them to reach temperature and as long as the sauce is fairly thick, serve on pasta. (I use 50-75g of wholeweat spaghetti but tbh any pasta will do)

If this recipe is clear enough to have worked, enjoy!