I start from this post for a question: so Unity DOES NOT create an atlas and make a single material of the meshes being batched, right? 
If I want to batch meshes with more textures I will have to work it out myself creating a large texture containing them all, right? 
right
and you can not use Unitys GUI system if you want batching, independent on how you do it, cause neither uses materials and no materials = no batching
Uh sorry but I don’t understand this last sentence… or maybe yes: you mean that each text block on screen will be a drawcall because of how Unity works?
correct, each text block, button, image, slider, … will be an own draw call.
the only thing in realtion to ui that batches are TextMesh if they use the same material cause they are really just normal meshes with a special function (render bitmap font)
Thank you very much for this other explanation… anyway, our game will have a very simple GUI if none at all during the game 
but good to know anyway!
By the way, you have a mail sent from your blog