export the contacts to a file on the device, then import the file and pick Google Account when you import.
But that will result in me having to go through and remove duplicates, and obtain new contact pictures for most of them.
I'll get it sorted, but it's a) a pain in the ass and b) completely invisible to a normal non-techie user until they are fucked. How I'd explain the above to my Mum I have no clue.