Hello I am a solicitor with over 15 years experience. I will try to help you with this.
You have been supplied with faulty goods which presumably you are unable to sell. This is a breach of contract matter. How were the garments described in the contract for sale or in representations prior to sale?
I purchased having seen sample garments 6 months previously which are only a visual representation not for quality. Yes, I am unable to sell them as have previously sold one before I was aware of the issue. This garment was returned by the customer who highlighted the fault and wants us to replace her bedsheets which have been permanently stained with the dye. These garments retail for around £300 so the quality should be impeccable.
You should threaten to bring an action for recovery of your £3,000 plus the extra cost you have incurred to compensate your customer. You should send a letter or email setting out the following: that you purchased the items from him, that you believed you were buying quality garments for sale to the public, that the quality of the garments supplied is wholly inadequate, that you are unable to sell them, details of the complaint you have received, that you want him to collect the clothes and refund you the money you paid. You should give him a time limit to comply (eg 21 or 28 days) and warn him that if he does not comply you will commence proceedings in the small claims court.
You can find the details of how to do this by following this link to the Government site on making a money claim. https://www.gov.uk/make-court-claim-for-money/overview. It is possible to go through the procedures on this site to produce a draft claim which you can then print fro the screen. A copy of an unissued court claim could accompany your letter to add force to your threats. However you will not be able to save the document you thus create so make sure you keep a copy for yourself.
Thankyou for the advice