Apologies if I am repeating anything already said. I haven't had the chance to read through all the posts.
Both of my kids started at Honeywell. My son was struggling as easy to be ignored in a large class. The teacher at the time didn't seem that interested in the kids who were not doing as well, so we moved him to an all boys private prep school. That school then got him tested and he is dyslexic, so we made the right decision as state schools don't have the provisions to provide a lot of learning support. He also got to do loads of sport, which he loved, and we watched him thrive, so I know we made the right decision.
We moved our daughter to a private school in Y5 so we could miss the bun fight for private secondary schools in year 6. She is much stronger academically but has also thrived.
On reflection, I would say that Honeywell is a great school, as long as your kids are bright. The parents (myself included) ended up using Kumon to help with english and maths, and there were a lot of Honeywell parents there whenever I went every week. We never used a tutor but I knew a lot of parents who were booked to use a tutor (or were already using one) by year 4. So you will need to be prepared to put the work in to keep your child on the ball, as the private schools and good secondary schools will expect high results in the entrance exams.
In Honeywell the classes stay the same all the way through the school from Reception to Year 6. Having seen the private schools change the classes every year, it means the kids end up knowing everyone in their year, and are learning to make new friends all the time. I found that kids in the same class every year could get very clicky (and so could the parents). Great if you get on with your class mates and parents, but if not, you've got a long time ahead. So much more refreshing to have a class change every year.
I was worried what the private school parents would be like. You are always going to get certain parents who are social climbers, but I was also pleasantly surprised to meet some really lovely, normal parents as well. It may also depend on what school you go to, as I do know some have a reputation for being very competitive.
Hope this helps.