I was in F LHR-ORD last week. The cart was blocking the only F lav because the flight crew was doing their back-and-forth thing. I went back to C and both lavs were occupied. I then went to the back of the plane to do my thing. Nobody waiting for a lav. It was a nice walk around the plane.

The announcement I heard was that nobody was to go forward of their ticketed cabin.

Putting your foot out to block the passenger? Pretty juvenile, if you ask me.