Wob – World of Books complaint: Unexpected customs charges

I ordered several books via the French website. No-where did it suggest that I might have to pay import or custom duties if the books (English) were despatched from England. 5 out of 7, if I remember correctly, were delivered without problem. For the last 2 delivered together, by the French La Poste, I was charged 10 euros import duty. I could not have the books without paying.
I contacted WoB who did agree to refund this amount, but on Paypal. I never used Paypal and do ot have an account with them, but I was told this was the only way to be refunded. I pointed out that I had paid by bank card, and would like the credit made to the same bank account but they insisted that they could not do this. I then asked if they could just credit my account with themselves, to be used against my next order, but no, they could not do this either. Paypal account or nothing, though they did say they would credit a friend or relative’s account. I find this unsatisfacory; if they can be paid by bank card they should be able to credit by this means too. I have twice requested a name and address to which I can send a letter, but the last time had no reply at all.
I would appreciate any help you can give me. It is not a large amount of money by any means, but the principal is important.