I said it in the first article about this, and I'll repeat it in this one. Email your MP's and let them know how outraged you are by this issue. If enough people email their MP's the London Police will think twice before disrupting a peaceful and legal protest against the Cult of Scientology.
I've already wrote to my MP (Andrew George, Lib Dem, St Ives), I'm awating the little yellow envelope from the Houses of Commons with some "yes, this is terrible, i shall be sure to bring it up with the Home Secretary!", if enough MP's start complaining to their MP's, which in turn start complaining to the Home Office, the HO will have no other choice but to tell the Police "look, don't distrupt Cult demonstrations, we're getting emails and one threatened to send in the BOFH!"
Bill Gates, because the Cult of Microsoft is legal, and not a cult.