I am having a bunch of trouble with takedowns lately and am hoping you guys can help. Seems I am leading with my head and getting guillotined frequently. The problem is most pronounced when I shoot on a kick e.g. before B's kick gets over his hip I am shooting in, catching the leg, and as I step in for the throw B starts the guillotine and uses me to keep his balance.

Any advice would be much appreciated.

Don't shoot in before the leg/foot is over his hip.

Try waiting until the kick is fully extended(over extended) and shoot in or sweep the weight supporting leg.

Just make sure you are clear of the kicking leg.

Ex. A right straight kick, let it extend, dodge out to the left and take his left leg.

Posture is paramount when doing a takedown. When you are going for the takedown, your head should be right above your shoulders, and your shoulders should be above your hips.

When people are trying to guillotine me as I do a double leg, I look straight up at the ceiling.

Also, instead of throwing them to their back (i.e., landing in their guard) I dump my oppenent to the side (like Baiana) and land in side control or knee-on-belly.

just kick'em in the nards before shooting in.

it makes a big diference.