Our last TMM charter was 2017, so I'm not sure if anything has changed. But it was convenient to fuel up at the Conch Charters dock, which is just outside the entrance to TMM's base. We first tried to go to Delta, across Road Harbour, but that didn't work out. I think no one was around.
By the way, our most recent charter was with BVI YC, and they conveniently have their own fuel dock.
We just got back from a BVI trip with TMM too and I couldn’t have asked for a better experience. From the easy check-in to the excellent condition of the yacht, everything was spot on. Highly recommend them for anyone considering a charter down there!