Dear Evo7 and AerBabe,
As WhirlyBird mentioned under JAA 3 nm is the minimum for logging cross country requirements.
If you look in the new LASORS book in section A, Appendix A it gives you the defination of Cross Country flight.
Cross-Country Flight: Any flight during the course of which the aircraft is more than 3nm from the aerodrome of departure
Julian,
You are right too. Under FAA rules the cross country time is counted only if the aircraft is 50 nm from the point of departure and the wheels must touch down at another airport minimum 50 nm away. So if you were to go for a jolly for 100 nm and come back without a touch and go or landing, you cannot count it towards cross country time.