Send the extra information to the same address you posted your claim, make sure you add your name, address and NI number to each extra page and number the pages, 1 of 9, 2 of 9 .... 9 of 9.
Don't forget to send it by recorded delivery, check after a few days that it has been delivered and then make a phone call to check the information has been added to the system.
Gary
Nothing on this board constitutes legal advice - always consult a professional about specific problems