OK, I have a first working version of my survey data converter working, just in time for the Easter trip to Matienzo with the DistoX. Currently it can read survex data (.svx) files, and PocketTopo export (.txt) files. It can write Survex files (.svx) and Toporobot (.text) files.
The main two conversions I have tested are for using PocketTopo on a PDA with a DistoX, using Survex to process the data on the computer.
So to get existing survey data (Survex format) into PocketTopo, you convert it from Survex to Toporobot, and then import the Toporobot data into PocketTopo on the PDA.
You then survey some more, extending the cave using the DistoX and capturing the new data in PocketTopo.
Finally, you export the data for the new trip as text export from PocketTopo, and then convert this .txt file to Survex format using my program again.
You can then quickly paste the new data into your master Survex file on the computer and work with this as usual (which for me means drawing it up using Tunnel).
If anyone wants to try this out then PM me for a copy. I will be in Matienzo from 8th to 18th April, but may have access to the internet from there. If not, then don't be surprised if I do not reply during that time.