As I mentioned before it made it so much easier for me that I started texturing the mid poly model first. Even though the low and mid poly models are still quite different in terms of smoothness and detail it means that I can use the mid poly textures as a guide/reference and I can figure out the placing of certain elements for the low poly model.
A big difference with the low poly and the others is that I have not included a gun cylinder or a proper exhaust pipe which runs along the length of the main body. Instead I created a main body which is more extruded in some places than others. For example I tried to copy the rounded shape of the cylinder, to some extent, by moving the vertices of the main surface around. Having done this it meant that I had to be careful and quite meticulous about where the textures would be painted on. The exhaust and gun cylinder couldn't be textured separately this time but rather painted on to the extruded surfaces. Luckily this job was made much easier as I could use the mid poly model as a reference and so could place and paint the textures accordingly.
So there we have it... a full run down of the texturing process of each of the three poly level models. Woo hoo! First look into the concept of Levels of Detail and not a bad start I'd say.