The right of work for student coming here to study on tier4 visa had been withdrawn. You can now only contine to work only if you are directly studying in a regongnised university which are publicly funded. Students at private colleges have no right to work and those at FE colleges which are publicly funded have only 10 hoursto work.
MOST NIGERIANS I KNOW HERE IN THE UK ARE STUDYING AT PRIVATE COLLEGE BECAUSE THEY ARE CHEAPER.

SO IF U PLANED TO COME TO THE UK AND WORK AND SUPPORT YOURSELF LIKE MOST PEOPLE HAD DONE IN THE PAST. PLEASE CONSIDER ANOTHER OPTION.
THE LINK TO THE ABOVE INFORMATION

http://www.ukba.homeoffice.gov.uk/sitecontent/documents/news/summary-student-policy.pdf

The information you posted is correct, but it doesnt apply to all sets of people, the right to work for 20 hours for some schools is still preserved, and the right to get a PSW (Post Study Work visa) is also preserved, admittedly, it's much more difficult. It however does not take effetc until APRIL 2012.

You can read this for an analysis going forward.

http://www.hotcoursesabroad.com/study-in-the-uk/study-in-the-uk/has-the-uk-closed-its-doors