We must be unusual but our costs are nowhere near some of these. Dds are 14 and 11. Dd2 is heading to secondary in September.
We spend about the same on clothes as growing has slowed down and they are wearing things much longer. Dd1 is in year 9, she has had the same school blazer, skirt and pe kit since year 7. We have just replaced the shirts as they were getting a bit small. I got most of her uniform second hand in the first place. Dd2 I think will be more brand oriented, she likes her sketchers trainers and if she doesn't like something she will not wear it.
She has pocket money to spend going out with friends £30 a month for dd1, £10 a month for dd2 (she doesn't really go out without me)
We have Netflix, disney plus, amazon prime, crunchy roll and Spotify usually. (Currently stopped a few due to needing to save for a house move).
I guess the biggest expense has been the rent for a 3 bed rather than 2 as they need their own space now and aren't happy sharing.
Days out - we've switched free park days to free museum trips! If we need to eat out that is more expensive now its not childrens meals but we rarely eat out. And going to London I now have to pay for dd1 on the tube so adds an extra cost.
We recently bought ipads for school work, but they sorted old toys/clothes which I sold on vinted to pay towards them. They are both on sim only contracts with o2 £6.99 a month, then I bought phones from music magpie around £160 each a few years ago. Works out cheaper than getting a phone on contract.
My biggest bit of advice is to start managing expectations now. We have always bought second hand tech, clothes, toys, homewear. My girls know if they go second hand they can have more for their budget. Make up I don't buy expensive so once they start wearing it I certainly wouldn't buy expensive brands for them.