Smee if your ds goes to a state school, they can not insist he wears uniform at all. The law in this country is one of parental choice, which is why school info sheets about school uniform always say "We the Governors fully support the Headteacher's choice of school uniform, and request that parents do the same" or something similar. There are also Governing Body guidelines which say changes in uniform must be phased in and parents given ample notice, which I think has to be over a term, although don't hold me to that. I do however know absolutely that uniform at primary age is NON STATUTORY, I am very cross on your behalf.
cakes, but in the holiday request as you planned, with a note about school having changed the INSET date, copied to the Chair of Governors, the worst they can do is put an unauthorised absence against her name, which effects their stats, not your dd at all. If she had a lot of unauthorised absences then the Education Welfare Officer (Truant officer) would contact you to discuss the importance of education, this only happens when children are away for weeks.
I am embarassed to acknowledge that my profession has been overtaken by mini dictators, who are only interested in their league table results, and not the individuals they teach. I would and did authorise absences for children who went on holiday, or to see an absent parent, or away for family weddings etc, I truely believe that these events meet a child's social need, build their familial links, which help children to develop into well rounded socially improving individuals. How arrogant to assume that school is the only place children learn and develop.
Right will climb back off my soap box now.