Thanks to all of those bloggers who left comments about the Round Robin fabric. Perhaps I was being too hard on myself - like artists never do THAT.
I've decided to frog the Fair Isle sock and redo it. I have a problem with overabundant size when knitting socks, which is probably why I've never managed to knit a whole pair. Of course, it might have something to do with never checking the gauge, but I blame my tiny supply of DPNs and the fact that I always decide to knit something at a time when shops are closed. I've actually bought some smaller ones so now that I've mastered the intricacies of turning the heel, I'm going to redo the sock. Fair Isle is tricky to knit (that's why I started with it! beginners don't need to do EASY stuff!) to get the size right as there's little stretch in it.
Maybe I could force myself to do a more straighforward pair FIRST?