I'm based in London So I'm quite au-fait with London based re-sellers of vintage/used Hermes (being too mean to pay import tax from the big U.S resale sights like
Fashionfile,
Rebag and Therealreal etc )
I can only speak as a purchaser because I've never actually sold Hermes bags so I cant say who would give you the best returns.
Companies that will offer you a buyout price on the spot are Xpres, Designer Exchange and Bagista.
I would assume you would be offered roughly 50% of the price they sell them for so be prepared for that.
Another option is to sell at Auction..you would probably get a better return that way.
In London Chiswick Auctions have about 3 luxury bag and accessories sales each year.. go to their website and email their handbag specialist Popsi Kundi (I may have mis-spelled that but you will find the details on their site)
There is also Bonhams-They too have Luxury Bag and accessories sales based in Knightsbridge from memory their handbag specialist is named Meg but I cant remember her last name.
My advice..bearing in mind as previously stated I haven't actually SOLD bags at auction or via resellers (though I have sold designer clothing) is that if you don't need the cash now try the auction route.
They should give you a realistic estimate based on recent sales figures and many bags ( i know having missed out on several) go way over the lower estimate.
I would AVOID sites like Ebay and Vestiare Collective.
Good luck!