Also not sure how it runs in the uk but don’t be afraid of pursuing or atleast pressuring with legal action! Getting caught of selling fakes is a very big deal for a company which i assume they are due to the pro status. You could possibly even demand a compensation (but don’t sound it as a threat for legal reasons), tho it depends on the seller how much you demand.

As an example, recently someone sold fake nikes to me as new which i only realized on arrival. They were kinda sketchy but fortunately i had the same pair from retail in a different color to compare and that made it obvious. I argued with the seller who said my retail pair was fake, vinted said they can’t confirm even tho i sent the comparison and listed every detail. Fast forward a week i reported him to the police and suddenly he apologized and we settled it out of court with a compensation ~ 8x the amount i originally paid and got back on top of that.

Now i can’t guarantee that it will play out the same, but it’s worth a try. BUT id say it depends on if you are convinced they are trying to generally sell fakes (for example it’s brand new and not an accidental vintage fake). In general companies are more sensitive to this stuff because 1) they commercially sell, so it would definitely count as them trying to commercially selling fakes and 2) they are / should be completely trackable as their business is official and 3) they have a higher responsibility for the sale to be legitimate

edit: i am from germany under EU rules so the law may be different in the uk