I agree with SXB on this. If I'd have an extra £1200 to spend on a trip then I'd definitely go C.
I do not know if AF have flat beds, however on such a long journey it would really help. You can take proper rest during the flight, making the jet-lag more bearable and you'd feel fresher when you disembark. And not for a moment do I underestimate the fact that you could actually put your feet up and help your body cope with lack of movement/pressure at 6,000ft.
I am not a fan of AF food I have to say, while I know that WTP's food-despite it's the same as WT-can be yummy (it all depends on taste and rotations I suppose!) but I'd rather have more space around me with worse food than the other way around!
Both CDG and LHR can be absolute nightmares to go through, so that wouldn't really influence my choice!!
Good luck and whatever you choose make sure you drink plenty of water throughout the flight - 14hrs on a plane can be very demanding on our bodies!!!
FBW