have colleges like kcl and ucl withdrawn from the intercollegiate degree programme? there is no such information on the websites.

Also, which school in london offers the best course in public int'l law?

2006-2007 was the last year of the intercollegiate LLM degree programme; from September 2007 the colleges presently participating will offer their own LLM programmes.
http://www.llm-guide.com/article/39/university-of-london-to-end-intercollegiate-llm-in-2007
http://www.london.ac.uk/95.html