The grants are discretionary, with each area setting its own rules. You can find out which authority is responsible for your area by entering your postcode here:
http://local.direct.g...school+clothing+costs
When I was teaching in a secondary school, the local authority's policy was that they would only provide a grant towards clothing when it was necessary to purchase a school uniform. (That has some logic behind it, in that they were only funding the EXTRA cost of sending a child to a particular school, rather than funding their general clothing). Our school had no uniform but, by officially declaring that the school's policy was to prefer red and black clothing (even though that statement had no real meaning whatsoever), it meant that qualifying parents could claim the grant towards their children's clothing.
The people who'll know if their are any 'little quirks in the system' like that aren't officials in offices of the local authority. They're the teachers in the child's school. (Even though most English schools are now on holiday, many headteachers will still be at work next week. It might be worth phoning the school,or calling in).
Chris