Don't forget the background to this, Roz, that is, the Faustian pact the Lib Dems made with the Tories: give us a referendum on AV (which we're sure to win) and we'll agree to your proposal for fewer MPs (to save money, of course) and therefore larger constituencies (which, as a side-effect - quite unintentional, of course - will result in more Tory MPs, but we can live with that).