So we want to set up our website to accept orders from outside of the UK too, however, when we go to do this the US or Canada shipping overides the UK shipping settings and doesn't allow a customer in the UK to checkout.
Hyde here from Shopify. I can see that we've spoken before about this issue.
I will need a little more information to better understand what is going on. In your last forum post, you provided a screenshot of your US shipping rates but then went on to say "though we had to delete the rates for USA and Canada as our customer in the UK wasn't able to proceed with the order". You also said, "I removed 2 items from the shipping rates for USA and Canada but kept them on for UK. Still had issues."
I would need screenshots of your US shipping zone set-up, your UK shipping zone set up, and if you have locations enabled, I will need to see a screenshot of your locations tab too, please!
This way I will be able to compare and contrast what is going on and get a better sense of how to advise you.
All the best, Hyde.