Had similar experience in USA a while back. As usual, I boarded early so my carry-one could go into a locker, which it did. I was in row 2.
At the very end of boarding two a**holes in Row 1 board (bulkhead seat), with much carry on. No seat in front, no room in overhead lockers. FA looks, but as usual bins are chokkers. I watched all this thinking: serves you right for boarding last with max carry-on. But was surprised for what happened next.
FA asked me if they could put the guy in front's carry on under his seat - ie in my legroom. I declined. FA asked again, asking me to co-operate. I explained that I had boarded early to ensure my stuff was in the overhead locker and didn;t want to be inconvenienced by some-one who didn't plan similarly.
FA asked again. I declined for a third time, looking them right in the eye. They went elsewhere. A**hole in front reclined the entire journey.
100% of the real estate defined by the metal hoop down there. Any feet from behind that extend beyond the hoop are fair game.