Buyer only has to pay the price you put on your listings, and unless you offer a choice cannot select a service you do not quote for.
If buying through ebay, which I would not recommend as Courier charges are not fixed for all parts of the UK like Royal Mail, so if buyer is in the Highlands of Scotland for example the cost can be up to 3 times what you have quoted.
Simple Post in my opinion is far from Simple, and sellers should always work out their own postage cost rather than follow ebay’s guesses, and find postage is underpaid.
