Hi guys, thanks for the replies....I received a reply from the tech support via the ticket thing you do and their advice was perfect - i'm all back up and running and very relieved its sorted without any sending it away to be repaired and the resulting expense.
For the possible benefit of others encountering this issue here's my reply from Line 6 tech support which did the trick for me!
Hi, please do the following: 1. uninstall Line 6 Updater, the driver and HX Edit via the uninstallers: start/ settings/ apps/ apps & features. 2. download/reinstall HX Edit v2.90 only! (will also automatically install Line 6 Updater + driver): http://line6.com/software/ Select all components for the installation. 3. connect the Helix via USB to your computer. Use another USB cable and USB port. Don't connect to an USB hub. 4. power up the unit while holding the footswitches 6+12 (until "entered update mode" appears). 5. shut down all Line 6 software including HX Edit, or any programs that use audio, like DAWs, iTunes, Spotify, video games, etc. 6. launch Line 6 Updater, log in, then reinstall v2.90.