PPL 21 days
Hi.
Have to be honest, your chances of completing it in 21 days are extremely low, near impossible these days. There are so many factors that will need to go in your favour - weather, m/t, availability of planes, instructors, your aptitude etc.
I went to the States two years ago thinking I could do it in approx 21 days and it just doesnt happen. Took me five in the end.
However, there is no doubt that you get it done in 4-5 weeks if you have completed the ground exams beforehand. Not only will these ease the pressure on you, but you will be able to focus on the flying a little more and should also have time to enjoy yourself.
Good luck.