To get Writing Thesis Visa you will have to fulfill further criteria other than the basic fundamentals set out by the United Kingdom Immigration Authorities. You will have to explain that you are a Postgraduate student registered in an educational institution which is supporting your application. You will further have to demonstrate that you have not previously been granted this Visa to write the same thesis.
Grant one period of 12 months (not to end of month); second period may be granted where institution presents strong reason why thesis was not completed within initial period e.g. student suffered a prolonged illness or written thesis did not reach the required standard.
An exchange student usually stays in the host country for a relatively short period of time; often six to ten months, in contrast to international students or those on learn abroad programs which can last for several years.