Seems like we could use a long term solution to the naming system. How about a 10m grid, using the fort sides to establish starting lines? It could be spread over the whole site to include the North field, the fort, wherever. We could use a typical mapping coordinate system with say, A-Z on the y-axis, numbers on the x-axis. Then you can say work is in E15, or if you want more precision, could use 5m grid, or just divide the 10m grid squares into quadrants, ie: "trench opened today in the NE quadrant of E15".
I did a VERY quick version to show you what I mean (see below). Lines are not exactly 10m, but reasonably close, so you can see roughly how much it divides up the site. This system also has the advantage that someone at the site can measure things out from landmarks and tell you exactly where their trench is and can easily be placed on the grid. If people think this is a good idea I will volunteer to set up an image with an accurate grid overlaid on it.