To be honest I don't think applicants can really know what prepares you for the course, since they have no experience of it. I found the French course to be perfectly good preparation, Russian much less so. It depends how much work you personally have put in during the A-levels. Butterfly girl's advice is sound, I would suggest you do not really have to read the books in the target language, but doing so will improve your fluency. Watch films and read in both your languages, find out about the course, if you intend to do linguistics, know about the basic principles. That is crucial- do not go into your interview wanting to do linguistics and talk about what a "beautiful" language French is, for example. Know your stuff, and most importantly, know your grammar!