low kick, what to do?

Yeah a low kick/sweep will be harder to spot if they know what they're doing, but the angle of their leg means that the range is shorter than a normal kick, more like the range of a punch.
So the angles of attck will tend to be like a shomen tsuki or yokomen uchi with similar ma-ai.
How do you blend with them?

Beyond that, it's up to you which responses you make, but if they're on 1 leg their balance will be weakened.

Together with a friend who is 4. Dan JuJutsu we found this nice technique:
If he´s coming with the right leg for the low kick you enter, stepping forewars to his front side, left hand pushing toward his face. It´s important to take a good step forward ant enter into a quite low stance. If you could comfortably hit his groin, that´s fine. Then you use you right hand not for hitting, but to take his left leg away.

I want to say from the beginning that I've only been doing Aikido for a few months so I guess you should take this from the source. Also, I have a very poor grasp of the Japanese terminology, so I'm just going to say this in plain English.

A while back my Sensei was physically pondering this same issue with some higher dan ranks. (The rest of the class was practicing a different technique, but I couldn't resist taking a minute to watch.) I'm pretty sure this technique could work pretty well against most kicks.

1) He broke uke's ki by punching the inner thigh of the kicking leg. This would work against almost any kick, as opposed to an elbow which would be hard to get low enough for a low kick.

2) Sensei threw uke however he felt. He tried different combinations but I seem to recall that the most practical was to sweep around to uke's rear and do a simple throw from uke's shoulders.

Again, please pardon my poor vocabulary but I think you will get the idea.

Matthew,

You sound like a really nice guy, so please don't take this the wrong way...

Watch a full-contact match that allows leg kicks. You won't see anyone reaching down to low kicks with their hands. Well, they *might* until the other guy hook takes advantage of their hands being down and punches their lights out.

One of the many strategic benefits of leg kicks is that they *hurt* and weaken and eventually get the other guy to drop their hands thus opening their head for punches.

Don't take my word for it. Go out on the web and research what the competitive guys are doing. They have the very best of motivations to search out what works.

FWIW,