I have a Vauxhall Insignia. I've had the waterpump, thermostat, and housing replaced. It's still not getting hot air in the car. Also, had 2 sniff tests done and compression tests done, both passed? Any help would be better than none.
If you have temperature in your cooler then it's most likely the heater mixer flaps (either servo motors that steer the flaps, or the controller). On many cars you are able to see if the servo motors work, however you will probably have to remove some trim to see it.
Just google vauxhall insignia [year] heater problem, and you'd probably find some youtube clip or similar that helps you.