'Ship to UK only' settings not updating

A few months ago someone posted with the exact same problem I am having with International shipping, but the thread is locked and I can't reply there.

I have sold a few items to Europe, which I can no longer afford to do with the £10 DPD the cheapest tracked postage, and the Marketplace Facilitator Tax.

I thought they had slipped through from back along, and as I am not pro-merchant at the moment, I thought I would probably have to update them all manually.

I did a page of 25, laboriously un-checking all the international settings (quite surprised I had so many). 24 hours later, they had all come back again. Also, scrutinising it a bit further, I realised some new listings, which definitely did not have international settings, were also now international.

I searched the help pages and found that I can set 'global' settings (which I thought I had, because my new listing pages had been coming with the unchecked settings as default). I checked my settings, and the settings are on domestic only, so there is nothing to change there.

I had to cancel one order, which now leaves me with a 25% pre-fulfillment cancellation. I can't afford to get any more.

Has anyone else had this problem and worked out how to solve it? I am thinking I might have to use the inventory upload, but not sure if I can do that while I am not pro-merchant, and I am not very good at it anyway. I know as many will get rejected as get accepted