There's nothing wrong with the answer by sjwoods but I'd like to offer other ways I would prefer to say this:

My French for your English! In London

I'm 27 years old. ["girl" sounds like you want to imply some immaturity to me, this conflicts with the education you reference] I come from the French part of Switzerland (Geneva) and studied political and social sciences. I'm very curious and interested in many things such as culture, food, art, travel, etc. I like to meet new people. I will be in London for one more month! I'd love to find someone I could meet with maybe twice a week to practice my English and my accent! We can speak part time each language! I'm learning English because I need it for everything and I really like it too. I'm a native French speaker who'd love to help someone with his French and maybe know more about French culture! I'm looking for someone nice, available twice a week and who would like to speak about everything and nothing!:) Let me know!!! I'm waiting for your answer! Hope to see you soon! Virginia

My French for you English! In London

I'm a 27-years-old girl, from the French part of Switzerland (Geneva) who studied political and social sciences.  I am very curious and interested in many things like culture, food, art, travel, etc, like to and meeting new people.  I am in London for one more month! I'd love to find someone I could meet with maybe twice a week to practice my English and my accent! We can speak part time each language! I'm learning English because I need it for everything and I really like it too. I'm a native French speaker who'd love to help someone with his or her French and maybe know teach him or her more about French culture! I'm looking for someone nice, who is available twice a week and who would like to speak about everything and nothing!:) Let me know!!! I'm waiting for your answer! Hope to see you soon! Virginia