Oxford

Definitely LSE its one of the most renowned institute in the world.

200 will be the

please go through this link for more detail information http://www.eng.ox.ac.uk/study-here/undergraduate/applying-for-admission

Its 650 above as per the latest info. You may check other requirement here.
http://www.sbs.ox.ac.uk/programmes/degrees/mba/how-apply-mba/mba-application-requirements

Hi Leena, can you mention which level of study you are referring to ? In any case you may check the program specific admission requirements on the websites. However feel free to revert.

Dear Leena,
Eligibility differs on what you want to study, whether you want to study bachelor or masters. Irrespective of program you must have excellent academic grades and must demonstrate high intellectual capacity. You may share what you want to pursue or rather visit the websites for details.
Best Wishes

Dear Ritu, you will find online application both the university websites. They also have the application checklist and documents you need to upload. Eligibility criteria varies again according to the program you want to study. Nevertheless you must excel in your academics as these are two of the world's top universities. I will suggest you first visit the websites.
Best Wishes

Hi Debasish,
The fees for the program and estimated living costs are mentioned on the department website. Here they are
http://www.ox.ac.uk/admissions/graduate/courses/msc-computer-science#content-tab-4
http://www.ox.ac.uk/students/fees-funding/living-costs/
Good Luck

Please qualify for gre or relevant test. apply in the university concerned and look for scholarship providing agencies on google