JICPOPS UK population estimates for 2018

Total population     66,469,578
  Adults   54,541,079
    Men     26,709,603
      aged 15-24     4,023,754
      aged 25-34     4,541,118
      aged 35-44     4,147,962
      aged 45-54     4,522,865
      aged 55-64     3,916,641
      aged 65-74     3,204,346
      aged 75+     2,352,917
    Women   27,831,476
      aged 15-24     3,811,536
      aged 25-34     4,473,821
      aged 35-44     4,212,127
      aged 45-54     4,654,611
      aged 55-64     4,051,652
      aged 65-74     3,451,139
      aged 75+ 3,176,590
  Children     11,928,499
    Boys aged 0-14     6,110,084
    Girls aged 0-14     5,818,415
Total households     28,277,508

Data with population, households and demographics within postcode sector are available from CACI