Hi Ollie just to agree with what Melchett01 said, I went down to OASC in February and was really nervous about going but when I got there the camaraderie was awesome, we all got on very well and there wasn't really any sense that we were competing for places we all just worked really hard and relaxed together in the evening. This friendship will really help you settle in and make the teamwork exercises easier. All I would say is do your best and ENJOY IT! It was one of the best things I have ever done and I am still in contact with the people I was with.
Good luck,
James