I forgot to mention that a member at the Brighton meeting was wearing one of the garish red POPE NOPE T-shirts issued by the NSS. There is a "Protest the Pope" march and rally planned for 18 September at Hyde Park Corner from 1:30 pm. A contingent from the Brighton group are gathering beforehand at 11:30 at Victoria Station (at Starbucks near Platform 1), and Hastings members are welcome to join them (though I'm not planning to go there myself).
There was a debate on this issue at Conway Hall on 1st September between secular and catholic speakers. There is an excellent report of the debate on the New Humanist blog. However it seems the audience was already decided in its views and the question and answer session deteriorated into one of abuse rather than rational argument, though the arguments presented by the catholic speakers are pretty weak.