Working forwards from 1911 to the present day can be very challenging indeed, so don't think that you are missing something or doing something wrong!
Success depends to a very large extent on how distinctive your relatives names were. A really unusual surname can often be traced through BMD records. Unfortunately, full middle names were replaced by initials in the indices after 1910, and this limits the "spotability" of distinctive name combinations thereafter. The inclusion in the birth index of mother's maiden name after July 1911 and the indexing of marriage partners after 1912 are some compensation.
The odds are also better if they had relatively uncommon trades or were professionals of some kind. Street directories are useful in this case, and some professional bodies (such as those for accountancy and the law) may be of help if you are lucky enough to have those sort of ancestors.
Their attachment to a geographical location also plays a part - families that stayed close together in a village are easier to trace than those who moved around the country and/or lived in cities.
Electoral registers are of limited value if you don't have an actual address or a very small, defined area to search.
One resource which should not be overlooked for those born around the turn of the century is First World War records. Although many service records were destroyed in the second world war, the surviving ones, as well as pension records, are available via Ancestry. These are often very detailed.
As I said before, the really crucial factor is the family name. If you have a John Smith who worked in a factory in 1911 then the chances of correctly identifying his family back down to the present day are, frankly, very slim.