Every case is unique
I see what you are saying Mr. @ Spotty M, but we don't have all the information to say either it was, or was not extraordinary. For example the operator could have had the same day weather delays, atc delays, headwinds, etc causing them to call on their six or seven stand-by crews, then this one came along and they didn't have an eighth crew. IF that was the case I would say that it was extraordinary for them to require eight stand-by crews.
Situation is obviously different at an airlines hub and a non-hub. At EMA, which is not a hub for Squeezy, the airline won;t have the same level of maintenance support to fix a/c packs and they are less likely to have access to stand-by crews.
Geoff should get a response from Squeezy within the month. If he doesn't like it, or doesn't get it he should then go to the AUC. They will look at all of the facts (and Squeezy has to give them) and determine if indeed compensation is payable under the regulation.
From what we do know it appears to me that Squeezy wanted to operate, made a good effort to operate, but failed because of the circumstances some of which were outside of their control. Do they need to take care of their customers? Yes - and it appears that they did. Now had it been Cryanair ...