Planning permission cost ?

[dal]

I am about to buy a house that is on a sloping site, I wish to put some decking outside the back door which I want to be level with the back door but due to the fact that the site slopes downwards the decking will need to be raised from the ground by approximately one meter, I understand that for decking raised more than 300 mm I will need planning permission, has anyone got any idea how much planning permission will cost and will it need to be inspected after.

Thanks in advance.