Around one street of London, the Strand, I found two places that would be the nearest of my perfect dream: bookshops with (almost) total accessiblity to the bookshelfs.
Directly on this street, around 400 meters to the East from Trafalgar Square (the one with Nelson mocking the French atop a column), on the left side of the street, at the 399, here you are, at Stanley Gibbons' shop. Here - French mostly, the others knew already through their catalogue editors - you will discover what a great stamp catalogue is: name and initials of the majority of the stamp designers, name of the printers, a huge amount of variations and errors described. For the printer, Yvert et Tellier catalogues very rarely give it. For stamps of France, it's normal because there was only one printer for almost all the philatelic history of France (but you need to possess one book that told you their name and periods...). It is not true for a lot of country and that can be important: first, knowledge is good, second, take a British definitive series that was printed by more than one printer in its career. Now, go see the prices... 1955 Castle series is a good example how the name of the printer is a price-maker.
At your hand, the British catalogues from the basic one (image + topic + price) to the specialised (tome 1: Queen Victoria ; tome 2 to be reprinted soon: from Edward VII to George VI; and many tomes for the Elizabeth II philatelic ocean). The Commonwealth catalogue (1840-1970) at 70 pounds sterling can be avoided for parts by countries or regions with the stamps until the year of publication. Coupons can be found in Gibbons Stamp Monthly magazine and special offers happened regularly to help empty the remaining stocks.
Better, at this ground floor, philatelic books await you: topical books or postal history (such as the Bahamas' by Harold G.D. Gisburn). If you have a precised title in mind, the nice (always) seller will go look into the stock or will take your e-mail or telephone references and try to find it elsewhere.
At the end of the shop, because the founder was a stamp dealer, you find the stamp counter with sitting desk for clients.
Don't be surprised that the stairs in the middle of the shop is going to another shop (of autographs), the London real property is so expensive that any means have been thinking to have a tiny place near the Center: use half a floor with access in your neighbour's property, to live at the bottom of the estate (with big curtains to avoid being a show for the pedestrians on the sidewalk above you), etc.
In a next episode of our London Season, an other bookshop whose competition to Stanley Gibbons is just one street ahead.