We have three instances of a form, on separate WordPress sites, that all use an Ideal Postcode plugin to assess whether or not a postcode is:

• In-Area
• Out-of Area
• Beyond Area

The plugin correctly assesses the postcodes, and for the Out of Area postcodes displays a disclaimer and checkbox to confirm registration as Out of Area patient.
However, the checkbox cannot be mandatory, because when made so, the field, correctly hidden by the javascript for In-Area postcodes, is invoked when trying to 'continue' to the next screen, and progression to the next screen is impossible until the In Area registration confirms Out of Area registration.
So we have no way to enforce the confirmation of Out of Area registration when correctly displayed - which seems improbable.
Can anyone help?
Here are the three forms:

1. https://www.holbornmedicalcentre.nhs.uk/clinics-and-services/services/registering-with-the-practice/
2. https://www.stphilipsmedicalcentre.nhs.uk/about-us/registering-with-the-practice/new-patient-registration-form/
3. https://www.holbornstudenthealth.com/registration-for-students/