Dip Architecture Part II for PSW ?

I've completed two years Dip Architecture Part II course this May, and the problem is the subject is recognized as a Dip rather than Master Degree even it is (or may should be) equivalent to a Postgraduate degree (MA or MSc).

I need another year or two in placement to complete my Part III study and I urgently need a post-study-work visa which will enable me to do so.

I’m currently doing a MA Thesis for 2.5 months for a master degree which ends in 31st Aug 2011. My visa will expire at the end of Sep this year. Can anyone give suggestions on what should I do to obtain this PSW? Except going back and apply outside of the UK.