Ive done some psychosis and self harm training and theyve got some great descriptions to understand hallucinations and self harm.
For hallucinations, try having a conversation with a mate about how your day has been, while another mate says random shite into your ear
youll only block him out for so long before your conversation goes to shit!!!
For self harm, write down all your coping skills for when you have a bad day, eg go for a drive, go to gym etc etc etc etc etc and then imagine none of them are available to you.
And with hospitals the problems arent just limited to NHS run/contracted ones but private too.