Do you accept a lower salary if you opt to work four days a week?
I don't think a 4 day work week is 20% less productive than a 5 day one, but generally 80% of a full-time salary in this line of work is still more than enough.
Also, it's pretty wild that you are effectively entitled by law to a 25% increase in salary if you have a child under 9.
That's incorrect. It's at a reduced salary.
If you're on a permanent contract and if your full-time function isn't in some way demonstrably critical to the business, you're also entitled to work fewer hours if you want, unrelated to children.
So I presumed, which is why I responded with disbelief to a commenter that sad (in response to a question whether salary is reduced):
> I would hope not. This article suggests that this is not the case
One is that you get exactly 1 week of paid leave.
The other is the right to take 26 weeks of unpaid ‘parental leave’ during the first 9 years, which is often used to e.g. start working 4 days a week (the leave is used at a rate of 1 day per week then; you could also use it for taking half a year off at once).
Personally, I only apply for jobs that let me work 4 day weeks permanently; I hate having to count how many days I've got left for whatever. (It's the main advantage of being a freelancer to me: no limit on how many vacation days I take.)