Firstly thank you to the people that answered my questions, we eventually bought one of the unused 2009 hull, 2011 engined Ribeye 500's that was mentioned on here. Ross Chivers and the rest of the team were very helpful and it was a pleasure to do business with them.
A VERY honorable mention goes to Leon at the Wolf Rock Boat Company, he was very patient and answered all of our (probably ignorant) questions. Most importantly he was committed to finding the right boat for us and (unlike some other places in the SW) didn't try to sell us something they had in stock if it didn't meet our requirements. Unfortunately we didn't buy a rib from them in the end, but I can highly recommend their high level of customer service!
Just can't wait to get on the water now!