1) It is possible to switch at almost any point (end of year, end of first term, end of first week) to another course in the law school if the course isn't right for you or your performance is not up to standard.
2) The course wasn't designed for bi-linguals. The challenge of the course is not on the ability to speak French, rather the intellectual capacity to be able to study two different legal systems simultaneously. The French language is simply a means to an end. Students frequently become quickly acquainted with the necessary skills and repetition and slow-speaking is common for the first month or so of lectures and tutorials. Having the ability to speak French fluently does not mean a student will do well at the course and, conversely, a lack of fluency does not preclude a student from doing well. One year, two students failed to pass the Maitrise, and they were both French. Having siad that:
3) You will gain fluency in French. By the end of three years in Exeter living and working in a French university will not be an issue, from a language point of view. By the end of the year you will, essentially, have become bilingual.
4) French law is very different to English law. There is a strict methodology and specific proceedures and processes to be followed. To succeed at studying French law a student needs to be motivated, well-organised and interested in the subject.
5) Qualifications. at the end of Year 4 you will graduate twice (presuming you pass all courses) First, you will graduate at the University of Rennes with a Master 1 (=Maitrise) as though you were a French person who had already studied for a Bachelor's Degree in France. Then you will return to Exeter for graduation with a LLB (called European LLB) as a Bachelor's degree in this country. (hopefully this means we'd get one of these!: http://justpaste.it/files/justpaste/epitoge-1.jpg (that one is for doctors - 3 stripes))
6) The Maitrise. There are two Masters degrees in France, a Master I and and Master II. They are independant degrees. Ordinarily, a French law student would gain a Bachelor's degree, and then apply for a place on a Master I course (as in this country) and then apply again for a place of a Master II programme. A Master I therefore is a complete degree in France, and everybody would know what it is was, just as everybody knows what an LLM is. (well, not everybody...)
7) The Summer. Try to read some French newspapers (Le Monde, par exemple) or Books in French about the Revolution, the Republics, the history of the political system of France. If you can get to speak French (in France, for example) over the summer then that's a bonus too.