UBS is a fine operator - small boats, personalized service. Depending on where you are staying on island may make a difference as to who you dive with. Prospect Reef has Dive Tortola, which took over the space that Baskin in the Sun had - they are very good as well. If you are staying near East End/Long Look check out Dive BVI at Marina Cay, they can be very flexible with their scheduling.
Other good dive sites are the Chikuzen (75' depth, seas need to be very calm to go out there), Alice's Wonderland (Ginger Island, 70' depth), P.O.S. (70' depth, Cockroach Island) and Wall to Wall (75' depth, West Dog Island). There are no dives deeper than 100' and there are plenty to choose from. I am an instructor on Virgin Gorda and am willing to help with any questions you may have...