Hi paul,
maybe you could be a little more specific about the area. For example the briancon/embrun area is really really nice. There you have the whole durance, the lower guil, upper guil, upper ubaye and so forth.
If you're giving it a go i'd sure get peter knowles guide to the South Alps, that has all rivers around this area in it. Make sure that you catch up with a rafting company or a shop before you put on somewhere, to check how the waterlevels are. Most of the rivers here are snow-melting water fed and the levels really depend on the temperature.
Have a good time!