From https://www.gov.uk/guidance/immigration-rules/immigration-rules-appendix-v-visitor-rules

“Study

25 Visitors may carry out the following study:

(a) educational exchanges or visits with a state funded school or academy or independent school; or

(b) a maximum of 30 days study on:

(i) recreational courses (not English language training);

(ii) a short-course (which includes English language training) at an accredited institution;

provided that the main purpose of the visit is not to study and the study is not at a state funded school or academy.“

Note: There is no mechanism to convert from visitor status to a study visa from within the UK.

From https://www.gov.uk/guidance/immigration-rules/immigration-rules-appendix-v-visitor-rules

“Study

25 Visitors may carry out the following study:

(a) educational exchanges or visits with a state funded school or academy or independent school; or

(b) a maximum of 30 days study on:

(i) recreational courses (not English language training);

(ii) a short-course (which includes English language training) at an accredited institution;

provided that the main purpose of the visit is not to study and the study is not at a state funded school or academy.“

Note: There is no mechanism to convert from visitor status to a study visa from within the UK.