Hi there
Ironically I am off there myself on Tuesday for a week.
I have looked into this before and the only way to become involved is if you buy a 20th share in an aircraft for some reason. If you get to the right place at the airport you need to track down Xavier. He has a share in an Arrow (or it might be a C337 actually) and is very friendly.
The trouble with places like that though is that all the aircraft have the third wheel at the wrong end and have propellers that have a funny blue lever to make them work.
Good luck if you are successful finding something. If you do please let me know and make a low pass over the house overlooking Isla Vedra on the South West tip of the island!
When are you going? I can't believe there are two British flying farmers going at the same time!
Bedlam...