That depends on each individual vendor's policy, which should be stated at the top of the page, under "manifesto".

So contact the vendor in the first instance.

If you can't work things out with the vendor, then you can start the dispute process.

orders are rarely SEIZED unless stinky uk:uk. you could receive a knock on the door from blue for a warning.
if it's 🌍:uk then you'll get a letter, or depending on the amount a visit. international comes with GREAT risk, would not recommend

You will always get the option to dispute after so many days.

The question here is would it be morally right to dispute it? If the vendors manifesto states about a no re ship, no refund for international then you yourself take the risk when ordering internationally and therefore knew the risk at point of purchase. In that case probably wouldn't dispute and take the L.

Always safer to order UK to UK only to avoid this happening

yes, the dispute system overrides any seller statement. your reputation and that of the seller is what matters every time.

How do you know it's been ceased ?

Whilst logged in, try to find the order confirmation screen in your internet history. Navigate to the order page and it should link, if it doesn’t try logging in from the order screen.