[Dyerryjex]

Yep, that's how phasing works. We consider two [main] ways of having an OBE, the traditional 'getting out of your body' when ready (which uses either vibrations or any other sign of deep trance to indicate it's time to exit) and phasing (aka Astral phasing) which is observing the hypnagogic state and using it as a platform for merging directly into an astral plane.
I recently spoke to a medium and yes, he uses the same method to achieve clairvoyance & communicate with his helpers.
As to what 'is not you', that's a little trickier- some metaphysicians consider the universe to be God in expression, and each one of us the same, therefore nothing is really 'not you'- but I know what you mean.
I always say- the form of your perception is not as important as the function. So you and I can go to a teaching temple and see different things (I seem to see universities and sometimes ashrams) or go to the Akashic records and see a room full of computers while I'll see an old-fashioned library, for example. But the function of the environment will be the same.
So whether the environment is self created (that is, of psychological importance vs. collective information) really depends on how well you know yourself and recognize your own mental/emotional states.