I have managed to get through in WsG... finally!!
I must have been standing too close to the invisible wall when I was trying to Blink / Displacer through it, and while searching for Exploration info for something unrelated, i came across an Exploration Turtorial thread by Wizard Trokair dating back to 2012. In the video, I noticed that when he was Blinking through walls, he was standing a short way off them rather than right up close. So, armed with that new (to me) info, i tried again and was successful
Cool to try, though probably wont again. Just happy I did it :P