Anyone who has previously researched ancestors who fought in World War I may be disappointed to find the limited availability of equivalent service records for World War II. The reason being that the records of Britain’s Army, Navy and Air Force are still classified documents held by the Ministry of Defence. Fortunately, there are still many collections that will help you find out more about your WWII forebears.
While many World War II records are still classified, there are still collections that can help research your ancestors.
If a member of your family serving in the British Army was killed in WWII, they should be listed in the UK, Army Roll of Honour, 1939–1945 record set. Perform a search, and if you locate the correct person you can discover the date they died, rank, the regiment they enlisted with, the theatre of war they served in (i.e. France and Belgium, Middle East, Africa), and the branch the person was serving with when they were killed. This is a transcribed series of records from The National Archives of the 171,216 casualties, so there will be no original document to view, but you can still save the information to your family tree.
Another record set from WWII that is freely searchable is UK, British Army Prisoners of War, 1939–1945. If your ancestor was captured by the enemy, searching here can help you discover their rank, regiment, prisoner number, the type of camp they were held in and its location. Finally, anyone with Jewish ancestors who survived the Holocaust, can search the names of over 60,000 people freed after the War in the record set Holocaust: Survivor names printed in Sharit Ha-Platah, 1946.
Although British military service records for WWII are still held by the MOD, family members can apply to get copies of personnel records by writing to the MOD. You will need the permission of the person themselves if they are still alive, or their surviving next of kin along with their death certificate.