You might try posting a new thread. You will get many responses.
Bus service between Breckenridge & Keystone is adequate. Night skiing is fun at Keystone. Still the U.S. is the land of the car, so a car rental opens up your options.
You will want to experience Vail, which is much easier to reach via car from Breckenridge.
Many skiers come from the U.K., and seem to be able to find great deals. I hope you do also.
Wear plenty of sunscreen.