I've removed Google Ads from the blog and I'm hoping this will prevent future pop-up adverts. Please let me know in the comments area below if you see anymore of them.
If this doesn't do the trick, honestly, I'm stumped. I have no idea what else could be causing them. According to my server's not-at-all helpful help page, it can't be coming from their side.
If anyone else out there can shine a light on this, I'd be grateful. Thanks.