I have recipes for chocolate cake, Maderia cake, lemon drizzle and champagne cake.
I want to increase the ingredients to make a bigger cake. Do I still use the same baking time and temperature?
When baking, try to keep the proportions of the cake's height, width and depth the same with the big cake as with the original recipe. I would start by increasing the oven temp just 25 ° F, and start checking for done-ness at the normal time, knowing that you'll probably need to go longer.
However, if you want a 2x sized cake, I recommend just making two layers of the cake, and sticking them together with whatever frosting or icing you'll use on the outside of the cake. You can remove a lot of the complexity by just baking two "normal" sized cakes.