Possible Clues:

• Lower chamber in building new, I recall
• Bordeaux site
• Sommelier's stockroom
• Spooner's plan to attract mods to Bordeaux store, perhaps
• Plonk down here?
• With half-scrubbed cleaner recycling bottles left for bottle bank?
• Temperature- and humidity-controlled place
• 21 down follows 24 down and plonks down here perhaps?
• Room that may be kept at 55 degrees Fahrenheit
• Storage space a tradesman provided after complaint expressed out loud