That is just the building contractors , if you add everyone else involved in the building industry , the building industry comes out top
By the end of 2020, the construction industry employed approximately 2.08 million people, a decrease compared to the 2.43 million employees in the first quarter of 2019. A large share of employees in the U.K. construction industry are men, according to the same source.
https://www.statista.com/statistics/432509/number-employees-construction-industry-united-kingdom/#:~:text=By the end of 2020,according to the same source.