http://thousandsc.blogspot.com/
It's exactly what it says it is: 1000 sentence correction (= 'SC') questions.
They're OK. In our official opinion, you should only dig into these in the unlikely event that you've already exhausted the Official Guide questions. And by 'exhausted' I mean that you've not only done them, but also established exactly why EVERY correct answer is correct, and, even more importantly, why EVERY wrong answer is wrong.