Thanks for the suggestions. Tried your suggestions previously at the weekend along with various others. Came home from work today, switched on ignition to run vag com again, and all is back to normal. The only error codes are obviously :
17978 - Engine Start Blocked by Immobilizer P1570 - 35-00 - -
but also
01561 - Left Rear Door 61-00 - Won't De-Safe 01562 - Right Rear Door 61-00 - Won't De-Safe
I'm wandering if these are linked, i.e short, voltage loss ,any ideas?