Hello and good afternoon, Izzy Williams, so please, like Drunkenelf said, take what I say with a little grain of salt. I love how much of a great sense of spaces and forms you got, especially your 10-minute poses, but those lines, shapes, and forces could use just a little bit more pushing and pulling, yet how would you please go for 1.5 hour of 2 minute sketch poses, all done using a thicker, darker brush? (45 scribbles, all flipped vertically, if our website lets you)
The two reasons are: 1) To help you be more bolder and confident with your lines and shapes, but to help yourself capture anything with as fewer lines as possible. 2) To help you see shapes and lines. For more info, please pick up a copy of Drawing on the Artist Within by Betty Edwards. And this video above the reply. Have fun practicing!!