The main Post Office on Virgin Gorda is kind of tucked around the corner & out of the way if you don't know where to find it. It's an obscure little faded pink building at the south end of Spanish Town. See directions below to find it, and attached photo.
For those of you who opt to stay at the North Sound end of the island, Leverick Bay is the best spot for provisioning & shopping. There is not only a full service resort & marina with the Chef's Pantry store, but a small mall with an art gallery, jewelry store, clothing store and another Dive BVI shop location, and several restaurants & bars.
See my VG Hotel Tips for Leverick Bay Resort for more details.
You must visit Aragorn's Studio if you get a chance on Beef Island's Trellis Bay. Aragorn is locally famous in the British Virgin Islands for promoting the arts & crafts of island artists and specifically working to promote the work of the few remaining native Carib Indians.
See specifics on my Beef Island page's Shopping Tips.
For information about the North Sound Express Ferry see my Transportation Tips for Virgin Gorda or Beef Island.
This is THE place to get whatever you need on Virgin Gorda, unless of course you are staying way over at North Sound. There's Buck's Market for groceries & sundries, Barclay's Bank, Dive BVI, the Wine Cellar & Bakery, the Bath & Turtle Cafe, and various small shops that carry jewelry, computer parts (with 2 internet access stations), clothing, souvenirs, etc.
You'll also find the BVI Tourist Board's information office here, though I can't say they really had that much. Still the ladies working there may be able to answer specific quesions you have, or help you to find lodging.
What to buy: I ws surprised to find that the cost of a decent UK bottle of wine really wasn't bad at Buck's Market or the Wine Cellar & Bakery.
There is a supermarket and liquor store plus several shops in the adjoining shopping center.
There is also capacity for 120 yachts
A good place to stock up on supplies