The 1939 National Register was the most comprehensive survey ever taken of the British population, carried out on 29 September 1939. This will in time come to be used to replace the 1931 and 1941 UK Censuses by family historians, as the 1931 UK Census was completely destroyed by fire in Dec of 1942, the 1941 UK Census was not taken due to the war. The 1939 Register has the added benefit of actual birth dates, and as it was kept updated until the 1990's, it also includes married names of the women who married after this time. Sometimes dates have been added alongside the married names, it is important to note that these dates refer to when the information was added and not the date of the marriage.
So far I have managed to add extra info such as d.o.b. and occupation for 1053 of the 1679 individuals in my index, these individuals have also been grouped by household which can be seen by clicking on the link found in the ref column.
An article about the 1939 Register can be found HERE