Went through rest of Francotoile pages and made changes needed to get the pages to validate.
Most errors were because the code was calling the version of the i18n:echo method that returns an element (which was an element in the wrong namespace) rather than the version that returns text.
A couple of instances of code producing tei elements into the output xhtml which of course didn't validate.
One instance where the html element included a style namespace which didn't validate and does not appear to be in use, so I commented out that html line and replaced it with a simpler one.