In a nutshell, how on EARTH do I get the Poly 800 to operate in OMNI OFF mode !!

As you found out, the P800 is always inOmni when you power up. All you have to do is go to the receive channel parm. towards the end of the list (appearance to the contrary, it is a global parm, not saved with an individual patch) and select it with the up/downs, that'll be the receive channel til you change it or power down (it's not saved, I don't think. I've got a mkII only now). Hope this helps.mn