Designing a Simple Lighting Circuit

For a college project I decided to do a simple lighting circuit, however the more I have done the more interested and the further into it I have wanted to go. I have now got an Idea that I am going to run two lighting circuits in one area and use an impulse relay to switch between the two.

I have done a drawing trying to show the circuit but I dont know if I have drawn it correctly. Am I going in the right direction? I have never done electrical drawings like this before so am unsure of the correct way to draw certain things such as contacts and the impulse relay!

<img src="http://i205.photobucket.com/albums/bb51/danny_utch/HNC%20Project%20Bits/scan0001.jpg" border="0" alt="Photobucket">

My next question is I want to work out what protection to use and what size cable. For example if I was to use 12 x 16W lamps on one of the circuits. What dictates what protection I use and where in the circuit it will go. i.e shall I just put some kind of trip on the whole circuit or on each individual 'branch'? off the live? Is there anything on the net that gives a good explanation of what I would need to do to protect this circuit and select the right cable sizes?

This isnt going to be built, it is simply me being a little inquisitive. Thanks for any advice/information.