I've turned the stopcock off at the meter before and that didn't shut off the outdoor tap but the one in the street does, so it's definitely on our supply rather than the neighbour's. I think it's a bit of a quirk of the old house and the way the land has been divided up, it was potentially a feed to an out building to begin with but that now belongs to our neighbour so I guess they just cut it off and put an outdoor tap at the new boundary. Then when the water meter was installed in the house it's at a point where the outdoor supply has already split off so now we've got a potentially unmetered outdoor tap.