Small update...
Looking at my jetpack stats from mobile (why has the link gone from the stats I see on my computer? VERY annoying indeed as I don't know how to get them) I have discovered that all the "extra" visits come from the US. I know this because the numbers more or less tally... I used to get something like 20 visits a day from there and now I get 1300... OK, my blog is compelling, but not that much (and it's not in English either :D ).
I wonder if there is a way to find out the IP addresses of the "fake" visitor/s to see who they actually are.
Hope this helps.
PS
Google's silence is deafening... I fear they are not really interested.