Interesting responses, some of you have had nothing buy joy.   
After 9 hours of various stages of updates I get the message attached, second attachment is from the log file.   
I then start DCS in some vain hope that the update has applied however am prompted yet again to download the entire PG DLC again.   
I am now going through another download (which is excruciatingly slow) that says 0% out of 3570.5 MB, yet another new number.  Based on the last attachment where it was 24gb of 10gb I can only guess how much this will download.   
Not exactly impressed.  My optimism is fading.