Ah, the old low front kick fake. Well, I admit that it works pretty good, done it myself a few times while sparring in TKD. One of the things I've gained from my sparring experience is the ability to judge (I don't like to use "sense", it's a little too sci-fi for me) whether or not the attack is meant to be a fake or not. This of course takes lots of practice and timing is everything. When the uke attacks using a round-house kick, I recommend entering toward the "belly-button" side of uke and at the same time it's important to use your (nage) hands to protect from any punches the uke might try. You can very easily take the uke off balance with a slight entering movement, similar to an iriminage. Well just an idea, take it for what it's worth.