I am going from what the woo-commerce support team has told me. They have logged into my site to see if they can find the problem. They told me they believe the issue is with the theme.
What you are showing in the screenshot was not previously showing before and is still not showing when myself or the woo support team use a BN11 post code – https://prnt.sc/125ri14
All I want, is for people in the few chosen postcodes, to have the option between the usual paid shipping that is available to the whole of the UK and the Free Delivery service that we operate.