Good advice and good call, Dermot

Sarah,
At the end of all of this somewhat bewildering input from so many different 'vested' interests, I hope you buy a catamaran that you eventually have endless fun with and whichever it is I doubt that it will be a decision you regret in any way.

Don't let Wouter's well intentioned but technical argument with Sparky put you off, don't let the anti-Formula, pro-OD camp put you off, don't worry about the "everyone else is sailing X, so I have to get one too" faction. Just weigh up (no pun intended) the pros and cons of your shortlisted design(s) and make your decision based on what YOU want from a boat, No-one will judge you for your choice