Can't move custom selection in UV edit window!

When I use a tool such as B or C to select parts of a UV map in the UV editor, hitting the RMB doesn’t move it like it does in the 3D viewport. Instead it moves the nearest vertice, edge or face/connected faces, depending on what button you have pressed at the bottom of the UV screen.

Those features are brilliant I have no doubt, but can someone please tell me how the heck I move a selection I make?

UV editing is utterly impossible as it is.

EDIT: Yes, I’ve done a few dozen searches in multiple places, but nothing.

Select, then G to move the selection, also from the UVs / Transform menu