As an addendum to this old thread:- If goods are marked as 'Zero value - Warranty replacement' could HMRC disagree and charge what they like ?

I have had goods (10 electrical sockets from China, which I paid $15 (£12)) and then customs wanted £8 Import charges and VAT and Royal mail added £7 handling charge. I refused the goods and they went back to China, who sent another lot, which came straight through.