Hi OP
.please trust the school! They are used to transitioning 30 kids who don't know each other, who are one year apart in age, and have differing levels of confidence and maturity. In reception its mostly play based, with maybe a phonics session in the morning and a maths one in the afternoon and the rest of the time its play. She will make friends in no time as there will be loads of others in the same boat and the teachers will look out for an include any kids that find it more difficult at first.
Playdates I found didnt really happen , it was parties the first year (not sure what the situation will be by sept). Millions of whole class parties every weekend. And there was a class whatsapp group, if there isnt one that you know of you can ask someone at a party and suggest one if there isnt. I think it's nice to concentrate on friendships out of school anyway in case of any issues in school.
People wear anything on the school run from loungewear to suits to smart. I dont know anyone that has specific school run clothes. Just avoid beachwear, swim wear and night wear and it will be fine. Yes I'm sure there are cliques in some schools but if there are there will also be other parents who aren't part of them and cant be arsed with the drama.
It would be mad to change schools based on who your child was friends with age 3 and 4. People move and children change so they likely wouldn't remain friends. The only difference it will make is an easier couple of days for your daughter in september.
Your daughter will be knackered the first term and will tell you she learnt 'nothing' and the only comments you will get are what she had for lunch.
The best things you can do to help your daughter are -
*stop worrying. She will pick up on it and think school is to be feared
- teach her independence skills, doing her coat and buttons and getting changed for PE and wiping her bum and washing her hands properly and drinking unpromoted (or anything else that's an issue when you dont remind her, like waiting too long to go for a wee etc)
- make sure when you play games with her that you don't let her win all the time, practice taking turns, and listening while other people talk.
This will help her settle in a lot more than if she spends all day clinging to the friend that she made at nursery instead of getting to know other people