@ilv1004s - you sir are a genius!
Turns out that my wife had a loose empty freezer bag which had been sucked out of the glove box whilst closed and then into that cabin filter space (and inlet above it) - causing a dramatic loss in airflow.
Using the instructions in the video to undo the glove box, boom saw it straight away, just yanked it out - (checked quality of filter but its still quite good) and boom we have air con again! Great news considering the next couple days forecasts!