Having read some of your previous posts on your plans I thought I would put in my 2 cents worth. We did a lot of research on these types of boats and too wanted to buy an older used RIB and fix it up for our particular needs. Zodiac has the reputation in the US and sells lots of boats to the Military and other agencies but I don't feel they are the best boat for what you are planning.
We ended up buying a 2004 7.8M Ribcraft and are in love with it. So much so that we have agreed to demo the boat for Ribcraft USA to potential buyers on the West Coast. You will be surprised at the cost compared to Zodiac and they are very well built. They are also lighter and I feel a much more comfortable ride. They also custom build their boats to the clients specs and you can get them with very little stuff and add things on your own.
We're in Ventura California and would welcome a visit if you are interested in checking out a Ribcraft. You can find pictures and some of what we do with ours on our website, www.channelwatchmarine.com
Feel free to contact us if you have any questions or want to take a trip to California.