Ok, well at first it seemed pretty full on but you soon get used to the pace of it. The days are full but we had plenty of breaks- the biscuits at Bekynton are amazing. It's just great fun really, what made it for me were the people I met on my course, some of whom I'm still close to and meet up with. The accommodation is pretty basic and not geared towards females (obviously!) but it's great fun and I'd imagine similar to living in Uni halls. The English teachers are legendary! Some are pretty eccentric (Marco in particular!). In fact tell Marco, Kate says hi! They are extremely knowledgeable but don't let that intimidate you, they are really friendly. One of them casually mentioned that he's friends with Ian Mckellen! The whole point of it I suppose is to support you in Oxbridge application and for me it was a real help. In our class I know of four students who got in to Oxford (there may have been more and many didn't apply), I sadly didn't but I made it to interview and the summer school helped me do it. My comp school offered minimal support.
Whatever you end up doing, ECUSS will be a fantastic experience so enjoy it!