excessive postage charged by online seller

I wanted to order 250 bookmarks to be printed by an online printer with a dot ie address but based in The Netherlands. I wanted to have them shipped to a client in Sweden. They were charging over €24 for delivery. I thought this was grossly excessive. I asked them how heavy can 250 bookmarks be?!
Interestingly when I put in Ireland instead of Sweden the del charge dropped to €9.
Their reply was that there were different charges for different countries and to check the price before ordering!
Is there any consumer type organisation I can make a complaint to?

I fail to see what you've got to complain about? The pricing is clear, it's not like it was hidden, you were able to see what the shipping costs were before purchase. Different shipping costs for different countries is normal, just choose a different supplier.

Overseas shipments have to be trackable (and usually insured) to protect the seller from spurious claims that the package wasn't delivered. That's where the huge cost differential arises, particularly if the vendor uses just one courier company because they can't afford the time to shop around and/or use a variety of methods.

No grounds for complaint.