[Your address and contact number]
[Reference: Goods purchased through eBay on dd/mm/yy]
On [date], I bought a [item] on from you on eBay for £[xx].
When I received the item I found that it was not as described. You described the item as [quote from how item was described on eBay] when, in fact, it was [explain why it was not as described]. As there has been a breach of contract and a misrepresentation I am entitled to a refund of the sum I paid to you.
If I don't receive confirmation that you will process a refund and that you will make arrangements for the item to be returned to you or cover the cost of me returning it within the next three working days, I will have no alternative but to raise a dispute through the eBay eBay Money Back Guarantee dispute resolution process.
I look forward to hearing from you.