Who pays for the Pope?

The row about the funding of the upcoming visit to the UK from the current Pope is bubbling up again (see here & here) The basic argument from non-religious, non-Catholic people is why should the general public pay for a visit from a religious leader of this kind so that he can proselytise and parade in a way that is of little interest or merit to the majority of people here. Clearly in addition to the shear waste of money this represents there is the added complication of the apparently vast and immoral sexual abuse/institutional cover-up scandals surrounding this organisation over the last few decades. I'm sure even Catholics themselves cannot be entirely happy celebrating this visit with such an unresolved cloud hanging over their collective.

The solution seems obvious to me, the estimated cost for the visit is standing at roughly £15M, there are 5M Catholics in Britain, a paltry £3 each?