Looking at your practices I noticed that your legs tend to be too skinny for the rest of the body, the rest of the anatomy is done really well though! I think that you might benefit now from drawing your figures larger, let 2 or 3 figures take up the whole page, you'll be able to notice your own mistakes better. I like the sharp lines that you are using, try combining some more sloping round lines with your sharp lines to create a more interesting figure. Over all I really enjoy your figures and think that are doing really well!
Anyway, i think these are great. The proportions are good in all of them but the first set (30s im assuming?) are a bit messy. The sketchy lines would work better if they had more direction to them. For the shading, I think you're on the right track but there are areas where it's hard to tell which is in the shadow or light. Here's a really helpful video on the subject!
Excellent session, Liam_P, however, I've got one small piece of advice: Can you do another 30 second sketch, all flipped horizontally, pretty, pretty, pretty, pretty, please???? The reason why is so, that, your figure poses will become more funnier and livelier than your last sketches. Hope it will surely so help you too much.