JAA IR Training
The only restriction is that you cannot take the flight test until you have passed all the exams.
Having said that most schools don't like you starting any flight training until you've passed them all.
On my experience I think they are right. Doing the flying is so tiring that it's really difficult to study as well. And if you were to fail any you couldn't then take the test anyway.
PM me if you'd like any advice.