Rita,
The big city firms, whether US, MC or wider city practices absolutely do not recruit on a first only basis so do not worry (if there are any exceptions here they are in a very small minority). They'll be some successful candidates with a first sure, most will have a 2.1. Many application forms won't ask for a module breakdown, simply to confirm the overall percentage. Do not worry about individual module grades, on the academic front what is most important is that you get a solid 2.1 overall (tick), and that your degree is from a well regarded institution (tick)
A first is a small advantage on an application, but academics are only part of the picture. What is far more important is to keep the extracurriculars going and try to build up legal work experience where you can during the holidays to supplement (and help you succeed in getting) vac schemes. Are there local high street practices you could work in for a week? are there legal teams or solicitors where any of your friends or family work that you could shadow?
& apply, apply, apply for vac schemes! They are competitive and it is, to some degree, a numbers game - the more you apply the greater the chance of success.