People have joined straight to France in recent years, it totally depends on the needs of the moment, new bases openings, etc.
For the upgrade, the process itself is very long, and you can start it after 6 months in the company. Plan on at least 1,5/2 years after date of joining to the end of command course line training, and that's in ideal conditions.
For France after upgrade, again, it depends on the moment. Last year some positions were available in FR for newly upgraded Captains, but be ready to move to LGW or LTN initially and join a transfer list, if you desperately want the left seat.