Summer Schools and Grades

Okay, so I'm the typical annoying person who's been worrying about grades and Unis for ever. Now it's actually getting close I'm worried that I'm not doing well enough and it's causing me to have panic attacks when I can't do something (I have an anxiety disorder anyway). My GCSE grades aren't terrible- 6 A*s 5 As and I'm predicted 3As 1B at AS but I don't know if it's good enough. Recently, people have been trying to persuade me to think about Oxbridge. Are my grades even good enough? I'd probably be studying Psychology (although if I can continue maths it may be Biomedical Sciences)

I've also been looking at Summer Schools but I have no idea how to write a good personal statement. Mostly looking at Oxford, Durham (Biomedical Sciences or Psychology) and Nottingham (for Neuroscience). I think Nottingham is most likely at the minute, since my grades aren't perfect. Thank you in advance,
purpleape