Hello Gabz and welcome to PSG.
Thank you for the tutorial.
I do have one question, while using the Pen Tool you choose "make selection". This defeats the purpose of using the Pen Tool since converting to a selection rastorizes the path. You also must use the drop down menu or right click everytime in order to choose "make selection".
Since your only creating straight lines, why wouldn't you use the Polygonal Lasso Tool? It will snap to the grid the same as the Pen Tool and it's use results in an immediate selection, thereby speeding up your workflow since you no longer need to make a menu choice as you do with the Pen Tool.
I do realize that the Pen Tool gives you the chance to alter the path before it's turned to a selection, but with the Polygonal Lasso Tool, the time saved would be advantageous and if you make a mistake, you can quickly hit Cmd/Cntrl + Z (step back) and then redraw the polygon. Also with the Polygonal Lasso Tool, you can hit delete to go back one step before the selection is closed.