So I've a z-wave plug which has become unresponsive to HE and presses of the physical button, after removing it from all automatons what do I do next only thing I can think is force remove as I can't get the device into exclusion.
Perhaps you've already tried this, but since you didn't specifically mention it: did you try the regular exclusion procedure? (I know, it's unlikely to work if the buttons don't seem to do anything, but it's worth a try.)
If so, then I can't think of anything else, either--a force remove (then waiting for the nightly cleanup process to remove the "ghost node" it leaves behind on the radio database) would probably be the only option.
Is this an actual outlet in the wall?
If so, this will never be deleted from the radio database until you physically remove it from being powered.
Don't assume that just because you can't see it, that it's not there.