So, if you click “checkout” without ticking the “I agree” box, you now get a popup like this:
and the popup has more room and can have different text to the checkbox.
You can have longer text for both of them, like this:
but that isn’t sensitive to what’s in the basket.
For Cert 18 films you might set up an Form Definition like this:
and attach it to the product like this:
and then when you are in the checkout process for the product you would get this: