OK - thanks everyone for the advice.
Im just back from my local high st travel agent. Had a good chat and ive come away with a handful of brochures, so i'll spend some time going through those this afternoon - and like you say, try to narrow it down to a few ships.
She also said that if just what to know what is the most popular cruise ship theres a site that collects comments and votes (over 15,000 votes!) from regular cruisers: Best Cruise Ship
Its not quite what im after as its not wedding ship specific - but at least it gives me an idea of where to start!
I'll let you know how i get on.