Ah! Was able to suss it out without having to resort to rot13-ing. I'd foolishly decided a certain move wasn't possible for the first missing 2 and the second 2 required such a feat of manoeuvring that I laughed out loud when I finally got it to work!
I think it's a case of spending too much time thinking I was missing something surrounding that one block that has sightlines to the big room and the last room, instead of being confidently logical.