Good post, Alatea. (btw, I love your avatar.)
Upon reading this thread, I'm thinking that I need to make a distinction in my mind between dissociating and "escaping to a safe place." I do experience a degree of derealization when I "escape", but not to a point at which I cannot function. I think that dissociation (not counting a fugue state, which is stark and scary) is when (for example) I suddenly go completely blank during a therapy session while discussing a painful memory.
I definitely will discuss with my therapist the difference between my dissociation and my (what I call) "Alice in Wonderland" disconnection from an anxiety-producing situation.