Hi there Hannah,
Thanks so much for your response. I appreciate you looking into this.
Just ran the test you asked me to do 3 times (just to make sure there’s no pilot error!) and the shipping options are not updating.
What I did notice, however, is that upon refreshing, the shipping zipcode field is being overwritten by the billing zipcode field.
What do you make of that?
Many thanks again for your help,
Mike