Well then no doubt you will campaign for catholic to be allowed to be Prime Minister of the UK then, something they have never voted upon, and seems to oppress the largest minority religion in the UK for several hundred years now.
I look forward to your campaign.
They're not specifically banned, there was just a law in place stating that a Catholic or Jew isn't allowed to advise the sovereign on matters relating to the church and as the Prime Minister essentially makes the senior CofE appointments by advising the Queen who to appoint then this could cause a problem... In reality it shouldn't stop a Catholic from being elected party leader and/or serving as Prime Minister - thought it might mean someone else has to deal with CofE matters AFAIK.