We're in same situation as Fizzy.
DD (4.5) starts full time from Sept 6th.
She's been going to the nursery at the same school for a year though so used to wearing the uniform (although now wearing the tie will be compulsory after half term when they start wearing the Winter outfit). She loves her summer dress so I'm pleased she can keep wearing it until October. She'd been going to Nursery for longer hours before that so going home at 3.15 will be a breeze for her. She can't wait until January when they start going to the local swimming baths - that will definitely be a highlight of the week.
Wouldn't say anything against somebody choosing to defer but I know that DD has benefited from already knowing many of her classmates in her nursery year and I think she would struggle socially if she didn't go up with them all at the same time.