I recently spent just over £2.5k on wood flooring and the underlay required (about £120 of the order). Because of issues relating to the sub floor, our builders never used the underlay however the retailer is now saying they will charge a 30% restocking fee for me to return the underlay. I paid on a credit card over the phone. Can I challenge this at all or do I just have to suck it up? Thanks for any advice!