you'll be fine! if you dont get into your firm and you end up at essex, you probs wont get towers, so maybe see about going for houses or wolfson court (which are slightly cheaper and more sociable than south courts).
Saying that though, Essex is so friendly even if you don't get along so well with your flat mates (if you're in south courts.. cos you will most likely get a long with most people in towers) there are so many clubs on campus you'll meet plenty of people anyways!