I teach yr 1. I think school starts far too early in this country. However, it does. I do not think you should hold your child back and wait until they go into yr 1. IMO, it will be detrimental to them. Yr 1 is a totally different ball game from reception. Apart from the work, the children will have already had a yr at school to learn social behaviour, school rules, bond with each other etc. I know that children change schools and fit in fine, but they will have already had the school experience.
Fairyblasset Your friend's experience seems way out of the ordinary. Were they at a private school? Reception teachers are well aware of the differences in ages and how it can affect children and will deal with it accordingly. Also, reception children do not get much homework, a bit of reading, maybe a little sheet to do, if that.
Reception is all about learning through play. It is fun for the children and they learn many important skills which they need to move onto year 1.
Also, for the past 2 years, the children in my class who were August birthdays were some of the brightest and mature children I have taught so it does not always mean that they will be behind. As far as I am aware, stats show that by the end of primary, young children have caught up with their peers.
I am sorry to have gone on, and at the end of the day it is your decision to make. However, I do feel that sending him to reception with his peers will benefit him greatly.