I saw a documentary about a man building a straw bale house. He used lime plaster. I have to use lime in my house because it is very old and is designed to let the moisture flow in and out. We cannot use modern paints because they trap the moisture in the walls which then makes them rot.
Lime is used for rendering inside and out, is a fantastic material because it bends with any movement of the building.
I use one part wet lime to three parts sharp sand to one part volcanic ash (forgotten the product name for it but it is for making it go hard.)
For internal plastering they traditionally put horse hair in as well for strength.
I cannot say how it relates to specific building regulations but it bloody works the walls breathe brilliantly and it is very long lasting.