Make despatch methods read-only/disabled in checkout

I needed to add some specific guidance text underneath the despatch method selection in checkout which I was unable to do. Therefore I’ve added it under the despatch method selection in the cart instead (and it actually looks better there) and the selected option correctly carries through to checkout.

However, I need to make the despatch options on that page ‘disabled’ so they can be viewed (and the user can see which one was selected) but cannot be changed by the user from the one they selected in the cart using the guide text.

I have copies of the cart and checkout pages in the child theme (exoplanet) but as it references other parts I can’t see how I can update the section to be read only.

Any ideas? I appreciate it’s a bit of a strange request but the whole project is a bit strange…