5mm will be more than enough and just use csm. Woven fabrics give their strength along the weave. They have good tensile strength but it's directional. You want strength in all directions. Use the 450gm csm (also known as 1½oz), it wets out much more easily and this is an advantage for your first attempt at laminating. If you are planning on finishing with gel coat, mix it 50-50 with normal layup resin and apply it with a roller. You must add wax to the gel to prevent it being sticky otherwise the surface in contact with the air will not harden. This is wax dissolved in styrene, not wax polish. You can buy flocoat specifically for this finishing process and you won't then need the gel. If it were me and I lived down the Ardnamuruchan road, I'd buy a bit more of everything and then it would be in stock for the next project.
A few days ago, in his thread, Slimtim showed the type of finish you will get.
When dealing with the csm, tear it rather than cut it with scissors. This will give you soft edges because hard edges will be seen in the finished product. Tearing csm neatly is a learned skill and an easy and effective method is to lay a panel saw on top of the csm and tear it upward along the toothed edge of the saw. Easy.
Good luck and don't forget to catalyze the resin!
Mr d, it occurs to me that if you've taken the trouble to make a reasonable quality mould, it may be worth using it as a plug to take a mould from and then you would have the ability to easily make more consoles in the future.