Flight delay

Roary_2

I had a 6 hour flight delay from Geneva to Southampton on 30 Dec. I wrote to the airline seeking compensation but the response was ' according to legislation such technical faults detected during a short time prior to the flight concerned are exempt under the extraordinary circumstances ruling'. What happened was the aircraft noticed a fault on landing at Geneva. They did not have a spare part so flew in another aircraft 3 hours later with the part. This was then fitted. The airline is UK based but because it flew out from a non EU country I am not sure if I have a genuine complaint and if I have what Di I do next?