Re: Becoming Instructor
I expect you will be going down the modular route if you just want to become an instructor.
So in order:
1) Complete your PPL.
2) Hour build to 150 hours total time to include 100 hours P1.
3) Study for and take the JAA CPL theoretical examinations *OR* JAA ATPL theoretical examinations.
4) Complete the JAA CPL Flight Course (25 hours if you don't have an IR) together with a pass in the JAA CPL Skills Test.
5) You will need 200 hours Total Time including 100 Hours P1 time to send your application for licence issue.
6) Take a Flight Instructor Course (125 hours theory and 30 hours training which can include up to 5 hours of mutual flying with another FIC student).
Steps 2 and 3 can be done in any order and can even be done at the same time.
As for the theoretical examinations. Take the JAA CPL theoretical exams ONLY if you do not aspire to gain an IR within three years or don't want to become an airline / corporate pilot. If you wish to fly for an airline then bite the bullet and take the 14 JAA ATPL theoretical examinations from the outset. If you do the JAA CPL exams and later decide to go on to get an IR or for an airline career then you'll need to take the JAA IR or JAA ATPL exams (as appropriate).
If you wish to instruct but NOT be paid for it then the only step you can leave out is step 4 (the CPL flight course, the exams sitll need to be studied for and taken but if you do this you will need 200 hours total time with 150 hours P1 before you can start the FIC course).