As far as I am aware, no further costs are involved. However, if you do require further instruction or help by an EG instructor towards the PPL theory then you would need to pay a per/hr rate which I am not aware of.
You might want to check that out, as far as I am aware (and have witnessed so far) there is no charge for any extra help you may need to assist you in your PPL theory. You could even ask the ATPL students as they are probably studying the same subjects!
EpsilonVaz