Its a very good idea to get the exams out of the way before going over.
But there are a few which can be done with no problem cold.
Air law, HPL, Comms, PofF and AG
Nav, Performance, Met are best done after a bit of flying/planning under your belt.
I also did the big cram in 3 weeks and to behonest you don't learn it properly.
So if ihad my time again i would study the 5 that can be done cold until you would be happy to sit them. Then off to naples and aim to sit them the first day you are there. then you can do the rest during the course as they become relevant.
Word of warning don't be sitting on the plane over reading PPL books. I am sure you will have all the correct visa's etc but best not wind up the colonials. All it takes is one of them to tip the wink to immigration and you will have no end of hassels.
MJ