Ian, Not sure if you still use a "live" copy of unicode.xml and hopefully there will never be a need to change the HTML character entity definitions but anyway....
The editor's draft of the entities spec has been moved to github https://w3c.github.io/xml-entities/ (The old URL at http://www.w3.org/2003/entities/2007doc/ redirects to the same thing) In particular this now means that unicode.xml and other source files are more easily tracked by other projects. (I know several browser and latex-to-xxx projects are using that in one way or another.) The sources are at https://github.com/w3c/xml-entities
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