Nik,
There may not be a smoking gun here. There is probably not a mansion in the Hamptons, or a bently garage under Warwick. I think besides kind of having every need met all the time and being treated like Gods while flown around the world.....the GB live a fairly simple existance in a nice apt in a building the fund they manage built.
They do however, hoarde large sums of cash. Its notable what the money is NOT spent on as well. Orphan cows research is some of the best on this board, and you will see when monwy is changing hands there always seems to be a winner. Its not perhaps as nepharious as the millionaire megachurch set......bit its not exactly squeaky clean either.