You said that you'll follow the airways in France. I know that Peter goes on about that a fair bit
but I've never seen any benefit in it.
I always make up my own route through France (pretty close to direct) and it's never been much of a problem. Stay high and you'll be covered by radar and won't have to give any strange town names as position reports
You might need to avoid the odd militiary airspace, but it will probably be closer to direct than you would be by following the airways.