You have to take the written exams in the same country as your medical. Your medical generates a reference number which later becomes your licence number. The flying syllabus is the same across EASA member states. Think carefully where you are going to do most of your flying. It is OK to move around a little but you will need some continuity particularly just prior to doing your test. It can take a while to get to know the circuit and local area of a new airfield, so although it is good from the experience point of view it will probably take more than the minimum number of hours to pass your test if you move about.