Tomas Restrepo is also investigating Moveable Type. Re his point about breaking current links, I plan to retain my Blogger-generated archive files alongside the new MT generated files. This maintains the permanent links to individual items, with any new linkings to archived items pointing to the MT archives.
I managed to import my Blogger archives into MT this morning - a case of not RTFM'ing (my excuse was that I ran in a 6 mile road race yesterday and was feeling pretty tired afterwards) and the problem with Mozilla was solved by removing the document type declarations from all the templates (I'll have to look into the implications of this).
The current state of this is here - but don't link to this or the RSS channel - I'll be changing the location this evening when I finish the migration.