This isn't affecting the UK only.
In the report it's mentioned that a minimum of a level 4 qualification from ICAO is required. As ICAO is represented by the local aircraft registries, there are certain countries, issuing up to level 6 qualification for pilots who have very limited knowledge of English, meaning their language proficiency certificate is not worth too much.
To work in international civil aviation, pilots and controllers are required to gain a Level 4 qualification in English from the ICAO.