I don't know what i did differently, but this is it, step by step.
-log into auteltech.com with your registered username and password.
-download pc suite v6.16 (NOT v6.17)
-place SD card in card reader, place card reader in PC USB slot.
-install V6.16 to SD card.
-place SD card in DS708
-plug DS708 into mains 12v adapter.
-plug DS708 into a LAN line (internet connection)
-switch on, and after initialisation choose UPDATE.
-choose V6.16 to install (NOT V6.17) and install it.
-follow on screen instructions.
My DS now works at this point. I've tried Ford, Renault and OBDii software on a couple of vehicles.
Next part of installation is as follows:-
-choose UPDATE again, but this time choose V6.17
-install V6.17
-choose UPDATE again, then all the subsequent Marques software that it lists.
Many thanks to Autel europe for their help, specifically Nick Goodman at nick.goodman@autel-tech.com