Alex, where you live at the moment is not a problem. i see you were born in Guernsey, that is not a problem either, but are you British?
You will also need 3 other GCSE Grade C or higher, or equivalent and 2 A-levels or equivalent.
Assuming you are British you could write to an AFCO and ask for information, I don't have a suitable address. Also you may be eligible for a 6th Form Scholarship to help during your final year in the 6th Form. To get this you would have to attend selection at the OASC.