You don't need to do anything at all. Throw any letters from schools or the LEA into the bin for another year.
Until a child is 5, they don't have to be being educated at all by law. (the whole starting school at 4 thing is just a big funding con by the schools - wheel the children in early and they get the funds for the whole year. OK, I'm being too cynical...)
If you haven't registered your child at a school, you have no duty to tell the LEA, the school, or anyone else how you are educating your child. If the LEA finds out about you somehow, they'll want to know (once she's 5) how you are fulfilling your legal duty to educate your child, and that's fine, and we can help you with how that works if you want it now or later.
As for getting in to school later - you apply whenever you want your child to go to a school. If it's a really over subscribed one, you might want to get your name down early for the following year. Otherwise, you just get in touch in the summer term when she's 5 or about to be 5, I guess, and say you want her to start in the Autumn when she firmly is 5.
I suppose there is a danger, if it's one of these have-to-live-within-20-yards-to-be-in-the-catchment schools that there will simply be no place available. But then, you wouldn't want to put your child in a school a year before she's ready and you're ready just to make sure there will be a place when you want it, would you? That would be crazy! But if it is that sort ofschool, I'd probably approach them in the Autumn when she is 4 (if you're wanting to start school at 5) and say you'd like a place next autumn in year 1 please and see what they say.
Don't let anyone pressure you into sending your child to school before she is ready, whether that's at 4 or 5 or 7 or whenever. THe schools want the children for the funding as much as anything - they are not impartial observers of your family situation.