welcome to the forum! I'm no expert in these schools but generally if you want somewhere you have to put it first, if you are not elgible then your second choice will then be treated as though it is your first.
There is some useful discussion about these schools and the order to put them in under the surrey forum a bit further down. ... I'll get the link in mo for you
Edit: here it is ... have a hunt through to pages 3 and 4 I think..