You will have to deal with two issues.
One is how you plan to support yourself for three months in the UK without working. They will look at the financial information you provide to see if that is a reasonable expenditure for a vacation in your situation. See Should I submit bank statements when applying for a UK Visa? What do they say about me? for some background.
The other key issue is establishing ties to your home country that will lead to you returning home rather than going underground in the UK at the end of your vacation. In general, it is difficult to explain why you can afford to be away for three months but not much longer. University studies can be a powerful tie, especially if likely to lead to gainful employment in your home country. You need to show why are willing to take a semester leave of absence despite being fully committed to your studies. For example, it may help if the courses you need to make academic progress are not offered during that semester.
Students rarely have the ties that are most reassuring to immigration authorities, such as a long term job paying enough to support yourself and any dependents. Do not commit to any expenses unless and until you get the visa.