It sounds like the offset of the discs is wrong, and they have supplied the wrong parts, rather than faulty parts.
The OP has every right to return the goods, extracting a refund for the goods and return shipping is another matter, and if the company is registered outside of the UK, that adds further complication - regardless of where the goods are shipped from, if the company is UK registered, that will help.
Personally, I think I would be contacting the seller again, clearly setting out the issues and demanding a resolution, and pointing out that returning faulty or incorrectly supplied goods is not time limited. Also be aware that some debit cards issuers can help with purchases, Visa in particular have a chargeback system for debit cards.
If the OP doesn't want to pursue it, his only option is to sell the goods on. If he posts any identification from the boxes he has, I'm sure we can do a bit of detective work to find out what they do fit.