Thanks @SpiritAdder I appreciate your thoughts, you're correct that I am worried about this; kids can be savage and I don't want her to have the same negative experiences I did at school, especially when it's something I can change.
The GP doesn't have her height and weight- I have her red book and plotted her percentiles myself. The general check the schools do in reception flagged this to me as well but I had the same attitude that she's "in proportion" etc. I had to buy some clothes for her from the Plus range recently and honestly I don't think that is normal or healthy.
I haven't cut treats completely- I think an ice lolly or a fruit jelly is a perfectly acceptable dessert, it's just not the chocolate biscuits/pack of sweets she was having before. These are reserved for weekends now. She has school lunches too which often include a biscuit/cake/bun or whatever so she's not completely without.
Also to be clear I haven't cut food or portion sizes, I've just changed things. So before where it'd maybe be a packet of crisps for an after school snack, it's now some veg sticks, hummus and an oatcake or something. Similar but different! This was actually brought about because she noticed she was still hungry after the crisps, so we talked about why that was and how different foods fuel our bodies. We still have crisps, just not as often.
I'm trying my best to foster a healthy attitude to food, exercise and taking care of our bodies and like pp said it's difficult to ask a child to make these decisions.
@SprigatitoYouAndIKnow daily. Honestly, at weekends, sometimes more. Chocolate biscuit with or after lunch, then something else in the evening. Like I said, it got out of hand. She's not actually overly bothered at parties etc, maybe that will change.