Add XS-Ribs to that list also. I went last year and ended up buying. One thing for sure is You will get a better price at the boatshow.
I think I heard Solent Ribs are gonna be there too, but I could be wrong. Expect most mainstream RIB manufacturers to be there, ie: Avon, Valiant, Zodiac, etc.
There are some photos from last yrs show here to give you an idea of what its like:
London Boat Show 2004
Worth going even to look at the engines!!
I'm going next year definitely. By the way International Visitors get a special pass to get in free if you plan to go more than one day and there is also an International Visitors Lounge!!