I've just got a letter from the LEA for my 3.5yr old detailing the primary application process - I have to collect a form and info pack from the nearest primary school from mid sept, fill in and return by nov to ensure I get considered for my choices for intake in sept 2006/jan 2007.
therefore if same procedure in your LEA, you'll have to do this in Sept 2008
check your LEA website as they'll probably be info for procedure on there