Same situation. As Gunpowder said, you might find yourself being left with one of the less popular schools. It would probably mean you have less choice about which school he attends.
So we did the thing: turned 4, catapulted into a full day at school -- to my son's profound detriment.
What I wish I had done at the time was:
firstly -- yes, get into the school you want at 4 for reception.
secondly -- see if it suits and how tired he gets
thirdly -- investigate exactly what they can do if you take your child out for odd days and afternoons
fourthly -- if it was too much for him , discuss with teacher and get half days until say, half term or Christmas
fifthly -- even if the school is extremely sniffy and cross about it, make sure your child has plenty of afternoons and full days off, possibly in some kind of routine to help your child, but if not then when you detect he particularly needs it
sixthly -- don't ever ever ever think your child ought to be doing x or settling like y or reading like z just because the others in the class are. To my shame I was sucked into this, my fault totally, and my son picked up that feeling and it was just awful. And never make him do reception homework if they give it and he doesn't want to.
seventhly and alternatively -- fight to start reception at aged 5
On the other hand, he might love it -- you never know. Some do.