DD is just 7yrs. She is age 7 clothes, but only just. M&S do 5-6yrs or 7-8yrs. DD needs 6-7yrs!! She is skinny, so 7-8 will hang on her, but I am worried 5-6 will be too small? I am buying online, what should I buy? it's the last part of school uniform needed. She has worn polo shirts up to now but needs a shirt/tie this year and I forgot until two weeks ago and everywhere is sold out when I go into store!