as I didn’t get TidyService to work correctly with UTF8 umlauts, I created a UNIX Shell Script wrapper for html tidy as it comes with OS X that does the job at least for TextWrangler:
open TextWranglers “Unix Filters Folder”
create a file named e.g. “Tidy Html.sh”,
paste the following lines into the file and save it:
#!/bin/sh
# …