Trouble is with sticking two fingers up and going on holiday is that you can end up frantically trying to get the kids to complete their final coursework submissions and finding out that they've lost their sketchbooks or they 'definitely handed it in electronically/is on their Mum's laptop' but it's nowhere to be seen whilst all the other subjects are pushing for interventions and dropdown days, before and after school revision sessions, etc, etc.
It never seems to be the kids who are well on track or above and submitting everything on the first deadline whose parents take them on holiday - it's the ones who are at best borderline for good grades or those for whom a pass in Maths and English and nothing else would be a fantastic outcome.
Subjects with a practical or coursework element are great for those who find sitting still and writing for over an hour nonstop very difficult - and for those who get anxious over it all hanging on performance on a particular summer morning. Even those who find writing easy, but are in danger of being overwhelmed by it can feel better if they know a proportion of their GCSE is already done and dusted. But that means they do not have spare time to go on holiday.
By July 1, there is nothing stopping you going on holiday until mid September. Christmas is normally absolutely clear. The Easter weekend is normally clear. But the others, including the Autumn half term, are likely to be important, particularly for those doing Art, Graphics, DT, Music, Music Tech and any other subjects that have a practical/preassessed component.
If places at 6th form were unconditional, it wouldn't be so bad, but many are subject to getting particular grades now, with no 'and if you don't get that grade, you'll go onto this lower level course instead'. I don't think it's fair, but that's how things have changed.
Talk to the school. See what they say - if they say it's fine to go on holiday in October, fair enough - but I'm not convinced that they will.