LookingForCruiser,
If you are interested at all in Gemini's I suggest joining our rather active Gemini Group on Yahoo.
It's free and open to all:
Gemini_Cats : Gemini Catamarans to sign up.
There is a file on the board called: Gemini New and Used boat pricing.xls - it gives the results of a fairly extensive review done by one of our members.
IMHO, the reason UK boats cost more is the VAT, and the requirement that the boat meet CE certification even if selling used.