Well the Cat-tunnel has been prepared, fitted, and removed. It was a bit fiddly as the builders hadn't quite lined up the holes on the outer wall and inner wall, and the plasterers had made only a rudimentary attempt at leaving a hole in the plasterboard.
An hour of cutting, levelling, filing, and test-fitting ensued. There was a new pile of plaster dust, but eventually it all fitted. GF has now removed it, ready for the painting. That's next, after he finishes his coffee.