LBS will love your multi cultural and international experience. But, thats not the only thing LBS looks for. If I were you, I would retake the GMAT one more time. 640 is very low and it will pull your application down. If you can get slightly above score, INSEAD will also be in your reachable zone.
I know atleast one person who got in with 650 at LBS. But, he had a extremely strong profile. It is not clear from your message about your strength on leadership and extra curricular activities, which are very important aspects of the application. I think you can get to the interview stage at HEC, Oxbridge, and Cranfield with minimal level of guidance. But, MBA is a one time activity. Do it from the best if you can. Don't get me wrong. Above schools are great, but I believe you can reach higher if you can work on your profile. GOod luck!
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