Ta all, though I have a set of cheapo generic diamond files already, and wanted something a little less coarse. In the end I went for a file that cost the same amount as the full file set from GW.

One swiss-made, #4 cut (dead smooth), pillar/flat Vallorbe needle file, from Shesto.com. Arrived this morning, and it is pretty smooth and very neat looking. I'll give that a try, and figure out if I should scrape a few more pennies for an accompanying #6 cut.
To be honest the new GW set probably would have suited my purposes nicely - being ocassionally trotted out to file parts of a sculpt flat and smooth - but in the end, although I wanted to, I really couldn't bring myself to give them the money...