You could do worse than speak to the head about this. The school could authorise the absence, doing so would not necessarily set a precendent, the option to fine parents for unauthorised absences has always been there but in my experience this option has not been excercised in the past. I would assume that it would be implemented with a little more rigour for repeat offenders. Speak to them, but respect their decision, or be willing to stump up if you chose not to.
I do feel your pain, my partner teaches and we have 3 children of school age. To go to Greece say, even for a week, in the summer holidays would end up costing us in excess of £4K. So we ‘make do’ with France or Spain, driving and camping. What needs addressing here is the greed of the holiday companies, not the fact that the government feels it should impose rules to educate children. Teachers teach, they don’t implement government policy.