I would use Polish foods instead of British, e.g, sausage
I recommend British (or Irish) sausages. They make a difference. And I'd use ordinary mushrooms (pieczarki). Home picked are best but any will do.
Lean bacon (Lidl sell an approximation of it) works best.
The beans are optional and the egg shouldn't be overdone. Fried bread is traditional with it but not healthy.
In London they often have their southern version of bubble and squeak (they do it like a patty down there). In the north we don't, but you can have fried potato (the precious night's boiled potato sliced and fried.
Lorna sausage is a Scottish alternative and easy to make at home.
It must always, but always, be washed down with a mug of very strong tea with a little milk.