Do you roughly know his birth date because someone might be able to look him up for you. You would also need it to get his army records. It costs about £30 but might help you as it gives the name and address of where he would have been living when he joined up. It would also have a more exact birthdate.
Start here with the army stuff
http://veterans-uk.info/recordsmedalsbadges.htmbut be aware that it takes quite some time to come through as they have had a huge upsurge of enquiries due to stuff ebing shown on the tv...
Dee