There have been many talented female British directors throughout the years, making it difficult to select just one as the "biggest." However, some notable and accomplished female British directors include:
Lynne Ramsay
Andrea Arnold
Sally Potter
Tessa Jowell
Gurinder Chadha
Sarah Gavron
Amma Asante
Clio Barnard
Joanna Hogg
Carol Morley
This is a subjective list and there are many other notable and accomplished female British directors.