Next of Kin Details ** See update below
The Ministry of Defence is very clear on the subject of Next of Kin.
The following list should be used when requesting Service Records for Second World War Service Personnel. Under most circumstances you will be sent a form to fill in and sign .The signature must be from the first living person in the list (Top to Bottom).
The form warns that it is an offence to knowingly withhold or to give false information !
If you do not meet any of these requirements then written permission must be sought from the next of kin and evidence of death (ie a copy of the Servicemans death certificate if he died after discharge from service.). A fee maybe appropriate for the investigation at the time of this update August 2011 it was 30 pounds.
!! Update to the above August 2011 - It would seem that for individuals dead for more than 25 years the MOD will release details without a pre-requisite for next of kin authorisation . Link below