Since I am pretty much done buying used records (I stopped after 15,000), almost all classical and the majority from many visits to the UK, here are three sources. I had several more over the last 25 years, but almost all of those are out of business - owners retiring or dying. Both of these specialize in classical records - lots of Decca, EMI and other top labels. Almost all originals (the occasional reissues are clearly indicated). No problem with returns.
Sophia Singer -
sophia@spiralclassics.co.uk.
Spiral Classics sells used and out of print Classical LPs by mail order catalogue worldwide. Many rare collectable and audiophile records.
www.spiralclassics.co.uk
She publishes an online catalogue with updates a couple times a year. I have bought from Sophia for many years. Extremely reliable. I visited her a few years ago - she is located in the English Midlands, and when I was visiting Mike Mailes (retired Grammy winning Decca engineer) and his wife near Sheffield around 2015, Mike drove me to visit Sophia who lives a few towns away. Prices are quite reasonable for what you get. Her stock list is arranged by price and alternatively by catalogue number.
Ambergreen is just outside of London, and I have only bought from them online. They have been very reliable, although I haven't bought from them in several years - my collection became too complete and I couldn't find any of my wants on their list. I think the owner's name is Pete but don't remember for sure. He did deliver a couple of my larger orders to my London hotel several years ago. I found they appear to be still active. Here is their website.
Ambergreen Classical is primarily dedicated to selling classical vinyl records.There are nearly four thousand on the sight ,all with thumbnail photographs and useful descriptions.
www.ambergreen-classical.co.uk
We didn't go to London in 2020 or this year, so I haven't been to my favorite walk-in bricks and mortar used classical (and other) browsing record store in London - Music and Tape Exchange. They are very near the Nottinghill Gate tube or bus stop. They used have a complete used Classical Music Store, on three floors, a few stores away, but this was consolidated into their main used record store at 38 Nottinghill Gate. The classical records are in one of the back rooms - it has moved from floor to floor over the years, shrinking in size. So I don't know exactly the size right now.
They price their records fairly and every month or two, go through and decrease the price by one pound. Finally, after it gets to 50p, they discard or donate them. So I usually find some records selling for a couple of pounds that I want. Over the many years (especially when they were much bigger), I would buy a few hundred records (mostly narrow band Decca SXL and postage stamp EMI ASD) for a few pounds each, and the occasional more expensive wide band groove Decca and early EMI ASD three digit record. They usually have a box or two of rarer and pricier records in the back that you have to ask to see. I don't know whether they do any online sales - I never bought from them that way.
Larry