Congrats on passing the tests... !
I was in ab-initio 28 which started in 1999 in Luxembourg. I don't know where you'll be living in Luxembourg. I stayed in a big house with different appartments, all occupied with people from my group. It was a fun nine months !
You'll get to know eachother pretty fast, 'cause you're all in the same situation. New country, new people, new carrer, etc... normally the ab-initio before you will organise a welcome-drink in one of the pubs in Luxembourg. You will get to know everyone, including the instructors there...they like to party too
You'll have plenty of time to do fun stuff with the group, allthough studying might take up more time approaching progress-tests...
You can look forward to an exciting time....enjoy !