Don't know where you get that information from Dave, as the pilots seats move forward and backward as well.
But the distance between MLG and nosewheel on a 320 is 12,64 meters. As such as long as the nosegear hasn't passed the taxiline you won't be on the grass. Which is visible from the stamp size photo as well.
As such the ground handlers must be pretty thick to push an aircraft with its nosewheel past the taxiline. I can only conclude that it has become a sport in LGW to do this.