Nice catch!. Yes they were French Army. They were visiting RAF Benson, Oxfordshire and also made a visit to Duxford, Cambridgeshire for a refuel/lunch.
Serials and codes
1411 DDU Puma
3664 GAF Gazelle
3850 GAI Gazelle
4019 GAY Gazelle
4233 GFB Gazelle
See following link from Duxford showing...