Where can I buy smaller sized uniforms?

[Fixitagaintomorrow]

DD starts nursery in September and needs a white blouse, grey skirt/pinafore and blue jumper/cardigan. She's 3 on 3rd of September and is quite petite, so far I've been to Asda and tesco and the smallest sizes they do are age 3-4 and they're huge on her. Does anyone know where I can buy smaller sizes? Thanks in advance.

I found Matalan and M&S were too big.

Tesco were great because they could be taken up and they had adjustable waistbands. Official school outfitters were great too as they had tiny sizes.