I delayed my July born DC. He is in reception now, rather than year one. It was the best decision we ever made. He was so emotionally sensitive and immature when he should have started school 18 months ago, still struggling to separate at nursery, worrying endlessly about the smallest things, displaying anxious behaviour, very low attention span etc. He also has a neurological condition that requires lots of scans and hospital appointments, so time off school. The extra year, already afforded to his autumn born peers,to mature a bit did him the world of good and he started school a confident, happy child. He is still sensitive and anxious at times, but it's manageable. TBH, I wasn't too worried about reception, it was being just turned five in year one that worried me. I don't think he'd have coped with the added pressure, but this September I think he'll be fine.
In contrast, we haven't chosen to delay our youngest DC, he starts school this September ant just four, but he is a totally different child, confident and adaptable, whilst able to concentrate and very eager to learn. Every child is different and I think that a more sensible and flexible approach to school admissions for summer borns is needed across the board, some children will be ready, some won't.