AF cancelled my flight
 

With the silly situation of having to take a flight every 18 months I had to book a quick jaunt to Paris to keep my miles in FB account active. I have just returned from holiday and seen an email from AF saying that they have cancelled my flight and re booked me on another flight. Problem is the turn around time is not sufficient and all other flights will leave me with an intolerable time in CDG as I have booked a BA return for the miles :D Do I have any recourse with AF for the cancellation or will I just have to grin and bear it?

Assuming your trip is in more than 2 weeks, effectively your options are accepting what AF offer, asking to be booked on some specific other flights that you would prefer (have a look at their timetable) or saying that none of those options are acceptable to you and ask for the ticket to be fully refunded.

Not an issue of recourse. Rather, question is what you want. Better to call in with a specific "ask" than to simply say that you do not like what they auto-booked you.

Problem with changing the flight is that I have a non flexible BA flight booked for the return

Unfortunately, that is part of the risk inherent with buying separate tickets. Airlines can and do change schedules. We might not like it but it is their right, and if they do so with enough notice (more than two weeks for flights subject to EU261/04 regulation), no compensation is due. Again, you can ask for a full refund, but precisely because of your inflexible other ticket, this presumably would not help either unless you can book with another company which timetable would be compatible with the timings of your other itinerary.