You're lucky it wasn't Heathrow where you were detained. Heathrow Airport is the stuff nightmares are made of. Coming from Australia, It's usually the airport you have to land. I've had two trips to Europe spending longer than 3 months. My plan was if I were questioned I'd play dumb - I am pretty good at it - and say I'd never heard of Schengen. Last trip I flew into Vienna ( the smallest international airport in the world I reckon) and when asked how long was I staying here, I answered 5 days. In actual fact I was staying 5 months but I took it to mean how long was I staying in Vienna. I have friends who go to Europe for 6 months at a time. They manage this by flying into Rome, and then not flying anywhere unitl they fly back to Australia.