But some of them have found to be in Europe
Bots are making most of the votes apparently. Not worth the bandwidth to look
Pretty clever bots if they give a valid email address then respond to confirm said email address. In order to do so they would have to have hacked millions of email accounts or create millions of new email addresses.
I'm not saying it couldn't be done, just that it is highly improbable.
I would therefore rank this as an excellent example of fake news.
I, by the way, am a British citizen who could not vote in the referendum because I am resident in Italy. I have not bothered to sign the petition because I think it a waste of time. I did sign the previous petition.