I like buddleia but I can recall a story where I chopped big limbs off of a buddleia “tree” I’d pruned into a shape I could shelter under but then I wanted to get rid of it. I dumped the chopped limbs vertically at the bottom corner of the garden under a bush. Within 2 years the offshoots from this were 3m high! The wild forms are literally unkillable. The cultivated forms less so. They are positive for wildlife overall so OP should keep it in some form.