I've had a couple of trips into Quiberon over the years: Always been able to speak English in the circuit.
Interestingly when I googled their website, there has been a subtle change of name of the aeroclub and the website revision dated 2009 no longer has anEnglish or German translation which I am sure there were before.
Menacing sign of the times?
PS While you're there a quick nip across the water to La Baule is a worthwhile trip.
Cusco