I complained by email, suggesting that the charges should have been mentioned before buying. I received a quick reply saying that the charges were not their responsibility, but was offered a 50% refund of the charges, if I sent a photo showing proof of the charges. I accepted this and got the refund.
I've since read complaints by other buyers, including many on the Facebook sites who have been caught by the same charges, and suggest everyone tries an email like I did.
Bottom Line: No, I would not recommend this to a friend
I thought the NatureFresh Bags seemed a good idea so ordered a few. They arrived today, two weeks after order placed, and that's fair enough for an overseas delivery.
HOWEVER, I have had to travel today to the sorting office and pay an extra £12.75 customs fee. I was not expecting that, and would not have ordered the bags had I known. The bags aren't the cheapest to begin with, and being hit with this extra amount makes them a poor option, even if they work!