History is history, and myth is myth. The beliefs that Mary Magdalene went to Provence and Joseph of Arimathea went to Britain arose centuries after those figures died. There is zero historical evidence to support either story.
I don't know what level you are in the Masons. But the fact that the masons that built the cathedrals to specification and were sworn to secrecy developed into the Freemasonary is not disputed.
Nobody disputes the fact that the cathedrals were built by masons, just as carpenters built cabinets and farmers farmed. The relationship between these working masons and modern "Freemasons," however, is tenuous at best.
Why do you think Catholics are not suppose to join, and are not welcome.
I have no idea what you're trying to say about Catholics. It is my understanding that Freemasons would welcome Catholic members, but the Catholic Church bars such membership.