How can I get an extended stay visa for the EU?

I'm going on a pilgrimage - walking from Canterbury to Rome - beginning September 1st 2011. I estimate it will take me and my comrades anywhere between 3 and 4 months to complete depending on how fast we move and how many multiple night stays we enjoy in bigger cities. I'm looking for a way to get an extended visa without having a home-base. Can you help me?