This is an Annex 6 ICAO convention requirement. The CAA part of this will not become mandatory, if at all, until March 2012. The CAA is also prepared to file exemptions in collaboration with other states. If, as seems likely, the French except large swathes of GA, then we will be able to go there and they will be able to visit us without Mode S. There is a meeting in December on this and the PFA will get an update, which I will post on this thread.
Thank you very much for this, Rod 1. It was just yesterday I was thinking about this very thing. I want to plan a trip, possibly to France, for summer 2008. My aircraft is permit, daylight VFR only, and doesn't have any transponder. It doesn't have room for a transponder and I don't know where it's going to go when we do eventually have to put one in!