Theland - // In hospital I found it extremely uncomfortable, and my face and nose felt bruised.
Thankfully I no longer need it, but wonder if the discomfort is a permanent issue? //
I would suggest that whoever fitted your mask did not adjust it correctly - it should not make you feel bruised, that means it is far too tight.
The mask should sit comfortably on your face, and when the air kicks in and makes a seal, you should not feel that at all.
I find the intrusion of air distracting, but perseverance, as my fellow wearers will attest, means you can get used to the feeling of the mask, and drop of pretty quickly once it is in place and the airflow is in action.
If you have to have one again, ask for it to be adjusted properly, you should find your experience markedly better than the one you had last time.