Version 0.0.0.3 (aiming low) of the ITunes Tag Helper is now available to download here. Two new features:
Remove files from the ITunes library which have been deleted from the HDD.
Add missing .mp3 files to the library from the HDD.
Usually disclaimer that this was built in a very short space of time and will probably crash on your system. It's only been run on Windows Vista and ITunes 188.8.131.52. Backup your ITunes library before running some random code against it.