Re: isolation transformer
domnic - A regular old xfmr (regardless of transformation ratio) is actually an isolation xfmr because the pri. & sec. are not connected to each other electrically. Pri. & sec. are linked magnetically.
The sec. of a regular old xfmr can be thought of as a "new electrical system" - maybe the term "separately derived" would be to your liking.
An autoxfmr, buck/boost, etc. is not a plain old xfmr.
In the world of marketing, the term "isolation xfmr" is frequentally used to mean an xfmr that also has some shielding, etc., added.