Assuming this was under £10k you can bring a small claim using the money online service. It’s pretty straight forward and the only cost is the issue fee- as long as you behave reasonably throughout, you generally won’t have to pay the other side’s costs if you lose. It’s primarily a breach of contract claim (and fraud but that will become complicated and I think take you out of the small claims track) so you have 6 years to claim. You will need to show - what was advertised/ described/ you believed you were buying, the invoice/ receipt/proof of purchase and then provide evidence from the jeweller as to what was actually received. If you can pull together that evidence, it’s worth a go - plus they may settle if they see you’re serious. Gather your evidence (screenshots of adverts/websites) first and then write a letter setting out your claim in full and giving them 14 days to pay and threatening proceedings if not. If they don’t, then crack on. Good luck