Geoff,
What you describe is;
1. Inbound aircraft 1 hour late due to 'crew problems'.
2. Aircraft pushed back, but returned to gate due to problem with air con (which isn't just about cooling the cabin air). This likely was a 'safety' issue. You want air with your flight, don't you?
3. With the delay your crew was close to, or would end up, 'out of hours'. Again a safety issue. (Fatigue being a significant topic of discussion here)
4. Couldn't find a replacement crew. Flight was cancelled.
If this is correct the flight was likely cancelled due to 'extraordinary circumstances'. I doubt that you would have wanted the aircraft to have been operated with u/s air con. and you probably wouldn't want the crew to be operating the aircraft without proper rest. I can tell you I wouldn't.
It appears that the airline did handle the 'care' requirements. i.e. fed and bed you, and rerouted you to your destination. The only real question is if this cancellation warrants compensation.
The airline has also tried to deceive you, which raises the suspicion level. Now it could be some min. wage guy who ise paid only to say no, no, no to every request, but then again ...
What I would do, is to put my complaint in writing to the airline, and copy the AUC (
The UK's Consumer Watchdog for the Aviation Industry | AUC Home) who is the UK N.E.B (National Enforcement Body). If you don't get a satisfactory reply in 30 days then follow up directly with the AUC. If the AUC agrees that the airline has an obligation to pay you compensation for the cancellation then they will push. No guarantee though, I would say your case is weak because your flight appears to have been cancelled for safety reasons, but we obviously don't know the full story - which the airline must give to AUC.
You can also consider (after submitting your original request and not getting a good answer) going to EU Claim (
EUclaim | Startpage). These guys have always seemed to me to be bottom feeding sharks, they do take a commission, but it might work for you.
I mentioned that the EU regulation is a 'dog's breakfast' because it is poorly written. I should have added that it is also a 'Zebra's lunch' as well because the EC raised SLF's expectations so high that may expect compensation for all flight cancellations. The original intent was to compensate passengers if/when flights are cancelled for commercial reasons - say only 10 pax booked - not to encourage airlines to operate when safety issues suggest that they should not.
Good luck, and keep us in the loop on what happens next!