Obviously to produce my final illustrations I will need to brush up on my skill level of illustrating as I have not had time to do much of this before this project. Therefore I shall list the resources I have used to increase my knowledge of drawing skills. I may add to this post if I come across any more tutorials worthy of noting.
Only Pencil: A great tutorial for how to draw the eye, with lighting and shading.
Stanislav Prokopenko: Not only is this a great tutorial on how to draw the eye, but from a whole range of different angles and takes you through each part of the eye that is visible in sketches in detail.
Designer Today: I found this tutorial helpful for getting the proportions right on the face.