If I understand the content of the two NEBOSH Diplomas correctly (International & National), the principle difference is that the International Diploma does not include U.K. OH&S legislation, since it is intended to appeal to OH&S practitioners from outside the U.K. that don't practice there. If you are looking to further your academic credentials, I would suggest your explore one of the graduate programs that are available. I have a Wiki I created here in Canada to provide information to OHS practitioners here on education & professional development oportunities available to working practitioners (http://safetyfossil.wikispaces.com). It is entirely non-commercial in every way. Have a look if you like.