i think in France, the sales system are all linked, meaning that your purchase data is all input into the French system (i know as my George V SA looked up what I bought at FSH). however, what Ken-doll is suggesting (if my understanding is correct), is that you can easily go to Germany, Spain or Singapore, Melbourne where there is no way for them to find out what you've bought in the year and purchase birkins or kellys.
i am going back to FSH again in september and will try my hands at either placing a SO or buying whatever I fancy on the shelf (birkins) and see if they'll let me buy a 2nd birkin this year! wish me luck!
p.s. i forgot to add that i purchased an ostrich birkin 30 and a HAC 40 at FSH this past June. So it appears that HAC sale is NOT treated as a birkin sale in H eyes! neither was I warned that I could not buy more. In fact, the SA was encouraging me to buy another Kelly!