English language requirements for UK doctoral candidates
If you are from outside the European Economic Area (EEA) or Switzerland, the institution must provide an assessment of your English language proficiency when it applies to sponsor you for a visa.
The level of English language required will be stated as part of the entry requirements by an institution you are applying to. If you are concerned about your language skills, you can ask the institution in advance about whether they can provide English language support (or other study support). Sometimes they will offer short courses just before the postgraduate programme starts, or during the programme itself.
For help with English language skills, see information on courses on the British Council's Education UK website or use their Learn English website to improve your language skills online, free of charge.