🚀 go-pugleaf

When i try to import formats (it makes no difference which formats) from a template file to a book file, it stops on some files with the error message "Can't reformat <document>.fm". However, if i open the file and use File > Import Formats it works OK. What's going on here? My book file contains about 140 files, so it's a huge pain to have to do each file individually. 
I also get the usual "unavailable fonts" message. I'd like to get rid of Arial (to Helvetica), Courier New (to Courier) and Times New Roman (to Times) from all my documents. Importing Paragraph and Character formats doesn't seem to get rid of them. ANybody know a way to do this. I was thinking of a search and replace in the MIF files, but i'm not sure if it's safe to replace "W.Arial.R.700" with "W.Helvetica.R.700" for example. What do the "W" prefix and "R.700" suffix mean? 
Thanks in advance for your help, 
Mike