I'm amazed at the obtuseness of many posters - this is a mother thinking 2 years ahead as she is already aware this may become a problem. In 2 years time she won't have a 2 year old she's "wanting to put into school", but a 4 year old who is still not allowed to start school for another year! And who could get bored and understimulated if she doesn't find a good solution that works for her family.
I have an early October daughter and really wished she could have started reception early (the fact sometimes rankles that she was born 2 weeks late and if she'd only been 2 weeks early instead!). Her brother is July and to be honest the issues he's had in school would have happened anyway in terms of his concentration and social skills, being old in his class would just have increased his frustration / exaggerated the differences between him and some of the others (very luckily we've been able to have him in an independent with small classes AND 3-4 other boys in his class whose abilities give him a serious challenge. One of whom is a late August birthday).
Actually, I remember when my son was informally assessed prior to reception entry, the teacher made us aware that they were able and willing to take boys into that class as soon as they were 4 (staying longer in the class though and going into year 1 at the normal time). Wasn't any use to us as his birthday was after the end of summer term. But perhaps showed that at 3 and a couple of months he nevertheless looked like he could cope with school "soon". Noting that independent schools can register for the under-5 preschool funding, which reduces the fees until the term after they turn 5. So depending on your location and resources, you might just be able to find him somewhere he can be in reception earlier as a starting point.
With my daughter we moved her to the nursery class of an independent school rather than keeping her in daycare because we had seen her older friends "outgrowing" that environment before they left for school. We had thought that we'd found a school that would "take the children where they were at" and work with them at their level; unfortunately (change of head perhaps?) that didn't really work out the way we'd hoped. While there have been some positives along the way for her being old in her yeargroup, there have been plenty of negatives, including not having much incentive to achieve more than she easily can (that's an issue with her personality as well. neither of my children are anything like you son sounds to be). She's 13 now and in a different independent school; by the way there is a child in the year below her who HAS been accelerated a year and still runs rings around his peer group; he's staying there till year 8 and I don't know whether he will go to a senior school straight after or what; I suspect there are options that will work out.
I do know a family with a child who sounds very like your son. 3rd child with bright older sisters that he was completely keeping up with. They were finding their local school worked well for him at least in the first couple of years, with effective individualisation where he needed it. I think he might be year 3 now and am not sure whether that's still the case - I tried at one point to encourage them to consider a choirschool as a route to a bursary and more individualised tuition further on but it wasn't right for them as far as I know.
As your son is in the 1st 2 weeks of September, you MAY find that you can get some flexibility from independent schools. Whether that can be matched in the state sector I don't know, and I think it is hard to imagine what the proposed flexibility to hold young children back a bit longer will actually do in practice. The oldest children in classes will be a little older, but probably not the real high-fliers whose parents may be desperate for them to get on and start school!
Mileage in schools varies enormously and unfortunately they can change rapidly. Keep you ears and eyes open, look around and ask questions of your local options. Be prepared to start with one solution and change if and when it is not proving suitable. Further down the track you will find that there are scholarships and bursaries in the independent sector, sometimes from as early as year 3, sometimes not till later. You may not need to investigate them or it may prove a perfect option.
Good luck and don't forget to enjoy your children!