They do have a location at Elbow Beach, but I think that is for shore diving only.
They will definitely store your gear at the Somerset Bridge location. When I was there, I took a taxi the first trip to get my gear there...subsequent trips were by bus.
A couple of suggestions --
Definitely send them e-mails with questions -- they were very responsive when I had questions before my trip.
If you are going to be there for at least a couple of days, you might want to consider buying a bus pass. I know they sell them at the airport, but you are coming by boat, so not sure where you would get them. You can buy 1, 3, 4, and 7 day passes that cover all zones -- definitely worth it since long 1-way bus trips across multiple zones can be $3-4. A 4 day bus pass will run you $35. If taking 2 bus trips every day for diving + additional trips for sight-seeing, it is definitely worth it. The bus drivers are friendly and helpful -- in fact when we were there, one driver drove us off of her route in the middle of a rain storm so that we could get off at a stop with a covered shelter. The Somerset Beach location is right on the bus line, just steps from a bus stop. The passes are sold at many hotels...there may be somewhere in St. George's where you can buy them.
Bermuda public transportation board:
http://www.gov.bm/portal/server.pt?space=CommunityPage&control=SetCommunity&CommunityID=252
Link to bermuda tourism site with info about getting around:
http://www.bermudatourism.com/default.asp?page=get_here_around.html
You can also rent mopeds of course (no rental cars in Bermuda), but then again it seems as almost every local you talk to has a nasty moped crash story....and after riding on buses and in taxis that drive inches behind mopeds along narrow streets, I can see why..;-)
Hope this helps.
-Chris