iPhone stuck on gestures (Pinch) screen - can't power off

Hi hi - My home button died a few days ago so I've been using the Accessibility version, the onscreen white spot.

While adding new gestures via the "spot", the Gestures menu froze with only the Pinch option showing in the top-left (but not functioning). The menu is now laid over my lock screen (my phone autolocks after two mins) and I can't cancel it, select any gestures, unlock my iPhone or even power it off - holding down the power button produces the regular "Slide to power off" bar but the Gestures menu is preventing me from sliding it.

I'm effectively stuck with an iPhone that won't turn on or off, with a full battery that's not going to die for days.

Has anyone else experienced this issue?

Many thanks. ^___^