Tonal Studies - Understanding Light and Shadow

I've always had a bit of a problem with value in paintings to get a sense of Depth. So I have taken photographs and desaturated them and done some speed paintings for practice. These are all pictures in Dundee and done within 20mins (this is due to the fact that after this time limit I found myself getting too caught up in details).

Starting painting, 50minutes.

Below the perspective was slightly difficult to establish simply by blocking in so  I then used construction lines in the sketch below this one and finally I could begin practicing.

20 mins.

20mins.

20mins.

This is an ongoing practice and I have taken notes in every image i.e. my intentions at the beginning with how I aim to do tonal studies, evaluate sketch. take what I've learned into the next image.