Archer claimed the country’s third medal in Poland with silver in the 1,500 metres, though was initially disqualfied before being reinstated on appeal.
The Cambridge athlete held her nerve at the end of a scrappy race to cross the line in second place behind Belgium’s Elise Vanderelst.
There were several episodes of pushing and shoving in a tight race and the judges deemed Archer at fault. An appeal by the British team was successful, although there was still the possibility of a counter appeal.
It did not take long for more British silverware, and this time there seemed little doubt about it as team captain Williams claimed bronze in the 400m.
The 27-year-old, who has moved up from the shorter sprints, was in fourth place coming into the home straight but produced a strong finish to cross the line in third.
Williams’ time of 51.73 seconds was a personal best and brought her a first individual medal at a major event since 2014.
Bradshaw became Britain’s third female medallist of the night with bronze in the pole vault.
The 29-year-old had hoped to claim gold but failed with her three attempts at 4.70m and had to settle for joint third alongside Iryna Zhuk behind Angelica Moser and Tina Sutej.
The three medals come on the back of gold for Amy-Eloise Markovc and bronze for Verity Ockenden in the 3,000m on Friday.
Additional reporting by Press Association.