I've been attempting to tinker with the England and Scotland events a bit to make some kind of branch to apply to things if England remains Catholic. I'm trying to be a bit more realistic here than I was earlier, so let's just say for a minute that Catherine of Aragon's first son, Henry, survived infancy.
To start the branch, an event could be created where Queen Catherine has a son and the kingdom rejoices. The historical choice is that he doesn't survive infancy, but you would have the choice of selecting that he does. If Catherine's son survives, Henry would have no reason to want to divorce her, thus he wouldn't have cast off Rome's Supremacy.
Henry would then go on to succeed his father as king (replacing Edward VI, and Mary I), die relatively young and be replaced by his younger sister, Elizabeth I (we'll assume Catherine was her mother as well, ensuring that she too is Catholic). Being Catholic, Queen Elizabeth wouldn't have any reason to start anything with fellow Catholics, so antagonizing Spain would be out of the question, and she wouldn't get involved with the War of Religions in France (Even being Catholic, I can't see England helping out their French rivals).
Meanwhile, Scotland's Reformation wouldn't have happened if England hadn't gone first. There simply wasn't the support for it otherwise, and it likely would have amounted to some uprisings that would be put down fairly easily. Thus, Scotland remains Catholic as well. Because Scotland's main issue with Queen Mary was that she was Catholic, they would be more forgiving of her complicity in the murder of her second husband. Thus, she wouldn't have been deposed. Since she wouldn't have been deposed, she would have likely remained the Queen of Scotland at the time that Elizabeth I died, and since England was Catholic and Henry VIII wouldn't have laid out his successors so as to avoid the Catholic Stuart line, they wouldn't have objected to her succession. Thus the Union of the Crowns would have taken place under Queen Mary instead of her son, James (Mary I could be revamped to be used in England, but it wouldn't be Mary Tudor, but Mary Stuart).
James I's reign likely wouldn't have changed much, except any Protestant-related issues wouldn't have taken place. The English Civil War would still happen, but religion wouldn't play a role in it. It would be purely due to a growing House of Commons becoming tired of Charles abusing his authority. Charles gets executed and is replaced by a Commonwealth. Etc. Etc. Etc. Charles II is restored, followed by James II.
From that point on, I'm unsure how to proceed...