As Sebastian mentioned Fly By Night, Deep Ridge, and Surrender To The City, I thought I'd chime in on the subject, as I have done many times here in the past.
These three songs are absolutely the fabrications of a wind up merchant that used to post here years ago, that went by the incredibly serious and credible name of The Left Testicle of Freddie.
The very first mention anywhere (online or otherwise) that I'm aware of of three purported demos from the Queen II sessions was in a post made by The Left Testicle of Freddie on 9 August 2004. You can find it here: link
If you care to look at the posting history of TLToF, you'll see that he burst onto the site with mildly believable insider info. Supposedly he was in contact with Brian's crew and the like, and he provided the kind of info that us fans love to hear. But his claims soon got more and more outlandish, and it became increasingly apparent that this was just someone having a laugh winding people up - and he didn't care who knew it.
By the time of his later posts, it was so obviously all a load of bullshit there was absolutely no reason to believe anything he'd previously said. And as he was the originator of the Fly By Night, Deep Ridge and Surrender To The City titles, there's no reason to believe they are anything but fantasy.
But, the internet being what it is, these made-up titles got around, and their origins were soon forgotten, or not researched. And incredibly, it got to the point where Brian even commented on his Soapbox about their non-existence. A fairly successful wind up, I'm sure.
(Oh yeah, there was quite a debate at the time that TLToF was actually Greg...).