After everything I've tried it turns out shampoo is the liquid to get rid of fabric dye from skin.
My son thinks this is quite ironic, because 'if you dye your hair, then you don't want the shampoo to get rid of the hair dye.'
Quite a simple answer really 'don't use fabric dye to dye your hair'
Well he thought it was funny. Guess you had to be there really !!!