In Uk weather 3 weeks is a bit optimistic and you do have to work very hard on the ground school in terms of self-study. On my course I would expect you to prepare at least 4 lectures or long briefings after receiving all of the basic core course on Teaching and Learning during one-to one ground school. Additionally the flying requirement is 30 hours and you should not expect to fly more than 6 days a week. Our FOB requires you to have at least one day off and the instructors certainly need it!!