I have an item listed in the UK and someone from America wants to buy it. I have no idea how this would work, especially as regards payment, and eBay charging commission on what will now be much increased postage costs. Does anyone have any advice?
You'll need to add your own shipping method and price to the US on your listing.
Bear in mind that there's also a 10% tariff plus £1.50 fee (50p if you buy the label via RM's website) if you buy a Royal Mail International label that you'll pay.