I would like to send a picture of my poor bonsai in the hope someone can identify what is wrong, thank you?

Those are Mealybugs and yes ofcourse this affects the growth of the plants as they suck the plants juice to survive. Controlling these strange bugs are different. The cottony was coverings on the insects and egg sacs protect them from sprays. Use a paint brush dipped in alcohol or neem oil to wipe off all the bugs. You find these pests underneath leaves, along the stems and particularly in the leaf axis, you can try a systemic insecticide. This can be mixed in the soil and taken up by the plant, which puts a toxin into the entire plant system. Insects that feed on treated plants are poisoned when they suck the plants juice. Read the label carefully and follow the manufactures direction for use before you mix the insecticide into the soil. Check out any hydroponic store for insecticides.