Yes! That's absolutely ok! It doesn't matter where you ride during the challenge month. Whether it's the winding French countryside, Swiss Alps or New Zealand's remarkables, it can all count toward your Great Cycle Challenge goal.
Just use either the Great Cycle Challenge app, Strava, MapMyFitness/Ride/Run or another GPS-enabled device to record your ride and upload it to your ride account.
Just use either the Great Cycle Challenge app, Strava, MapMyFitness/Ride/Run or another GPS-enabled device to record your ride and upload it to your ride account.