Well, I'm confident that if I'd actually installed it through Wine I'd never have had a problem, but instead I was trying to run it from my mounted NTFS volume at /mnt/windows. Obviously the EPC is meant to be able to find it's other two directories in C:\ (TMCxxxx), but with wine using ~\.wine\dosdevices\c: as a virtual C: drive, this wasn't happening. So I copied the TMCxxxx directories to my 'virtual' C: drive, chmod u+w them, because since they were copied from an NTFS r/o volume they were flagged read-only. This returned the missing text in the boxes. I just copied over missing .OCX files from windows\system32 to the virtual c: drive's windows\system32, and regsvr32'd them.
As I say, I'm confident that an actual install carried out through Wine would work perfectly. It's just that I don't know where my install images are, and with NetSupport having most of the controls missing from it's Configuration page, I presumed there was a more general problem with missing text/bits, but I guess not. NetSupport is still the same.