student visa extension; please help

Can anyone please advice for extending my student visa:
-My student visa was extended in 2008 for three years for doing self funded phd in one University. I started my studies but before registration(matriculation) I came to know my supervisor professor is moving to another uni and I will be placed under a junior level(lecturer) ; I accepted the offer as the prof. was renowned in my phd field.
-I changed to another university for doing Msc as the course director advised that all his previous students secured funded Phd after msc and I too have great chance. I passed out in 2010 but due to credit crunch, it was impossible to secure phd funding.
-I informed border agency about change of university in 2008
-Now I am joined in another university and applying for visa extension. In between I applied to about 15 universities without success.
-It was before PBS
-Should anyone comment any problem for visa extension.

Many thanks