Many thanks for your help Saratoga and Miikerman,this did indeed fix the majority of the issues.
My player was supplied with the MCP/MSC setting on “auto detect”, so setting this to MSC has at least stopped the files from being renamed and so on. Consider me schooled by the masters 
Sadly, the new Zip still lacks a very useful function that the Clip had - podcasts with both elapsed time and folders. Ill explain:
On the old Clip, it was possible to copy folders of podcasts into a directory called Podcasts. For playback, the only option was “Music”, then you could navigate to Folders > Internal > Podcasts and see the folders. Navigating into these folders and then choosing Play All resulted in the files being played with an elapsed time shown. This was very handy for rewinding to a certain point (rewind accelerates so can be tricky with only a bar graph to guide you) or for seeing how much of the podcast was left to play.
The new Zip doesnt work this way. For starters, you now have a selection between Books and Music when playing back. Choosing Books will get you a time indication (strangely, both podcasts and audio books appear in this menu) but no folders; while Music will get you the folders, but no time indication 
All of this testing will also get you a frustrated customer who would rather be doing something other than trying to figure out the nonesensical rules of the device he just bought.
In conclusion I guess I can live with loss of the time indication, but one bitten…
