I check in and out of Gun Creek all the time; it is staffed at regular hours, although I'd add 30 minutes to their official opening time and have never tried to do anything close to closing time. They still don't have a credit card machine, so everything needs to be paid for in cash. I usually anchor in Gun Creek temporarily in order to clear in/out, but they've never really looked for the boat so I guess that one could dinghy over from Leverick or from Prickly Pear. Note that you can't dock at Leverick and _then_ clear in; that would incur the wrath of the powers that be.
I find the two working there to be friendly and efficient and it certainly beats my experiences at the other BVI ports of entry.
I sent a picture of the building and anchorage to noonsite when they opened ... just a second... http://www.noonsite.com/Countries/BritishVirginIslands/GunCreek


After more than 20 trips I can say that the only time I ever paid more than $20 for clearing in was when I did my temporary import at the same time; even that is only around $200 for my 57 foot boat.