If a former serviceman served in U.K. armed forces after 1939 you currently need to approach the MOD to access their service records but I don't believe that they have to give anyone access to the records. This may change in time if the records are released to public records. On a number of occasions, I have tried to find the service records of former Britishservicemen who served in both WW1 and WW2 but have never been successful. I concluded that the WW1 records were most likely held with the WW2 records by the MOD but I have not pursued the matter by contacting the MOD to ask. I, of course, don't know this for sure but it has been true in all the case which I have looked at.