Dave,
you need to go out and do a survey and a burn test, see for yourself the fibre content you are dealing with.
Prochem fibre shampoo is sometimes used to clean upholstery you mix with water in a bowl then apply the foam that builds on the top of the mixture with a sponge.
Do you know whether the chocolate stain is from a hot chocolate drink or a bar of chocolate?
You may have problems removing without using protein spotters or de-browning products, and then rinsing.
Mark