A few years ago I bought a pair of Patrick Cox shoes, basically gold high heel, diamanté on gold straps, stunning on but the diamanté on the straps almost immediately started coming off after just one wear out one evening.
I’d bought them from a designer boutique called Question Air in Dulwich Village and when I tried to return them - as being faulty - I think the most I got out of them was that they’d return the shoes back to Patrick Cox, which they did, for them to be returned. This was back in early 00s and they cost something like £300 then. My then boyfriend who shopped regularly in designer shops (I did too, I had the money then and it was important to me!) was furious and thought I should’ve got a refund.
When I bought a pair of cream sandals from LK Bennett and changed my mind about them (despite spending hundreds of pounds there) I was offered only a credit note and didn’t return to shop there (or not for a few years anyway!).
My best friend at the tIme was a legal executive and always quoted Sale of Goods Act at shops when she returned a top she’d worn once, and made out it had a fault with it, (yes, I know that’s naughty!), I never dared to try that trick.
Even though I did buy or was bought designer shoes in future it taught me a lesson that not all items are perfect simply because they’re designer and cost more and sometimes like it seems in this case they send out an ex display or already worn shoes to people and hope they won’t notice!
I’d escalate this, Trust Pilot, Resolver (they resolved a Cafe Rouge dispute I had) and even my DM after being missold an EE plan got compensation and an escalation to executives office as she wrote a letter and emailed them to complain.
The big companies think you won’t dare to complain.
Go after them OP and good luck.