I beleive most of the pre war RAF pilots likr Bader, mistrusted cannons because of reliability issues. RAF pilots fired too far out with 303s in 1940, I dont think that was his opposition to the armament.
Im sure that the Spitfire IBs problems with the hispano 20mm in the BoB did little to change that view either by RAF squadron leaders. It wasnt untill mid 1941 that the hispano 20mm was viewed as a reliable weapon amongst many. Like all conservative organisations, air forces were slow to change, the RAF was no different. 303s were the tried and true (they just did the entire BoB campaign with them), and the 20mm was the unknown.
As for the clocktower story, never heard of it, but that wasn't Bader, I doubt he would have been so careless as to do something like that. He collided with a 109F and bailed out clean, minus one tin leg. He did indeed have dinner with Adolf Galland, and the two remained close friends after the war.