Can i take a transfer from a mid size firm to one of big 4?

I cleared both groups of IPCC held in November 12 in first attempt

Currently, I am working as an article in a mid-size firm but I am not happy with the volume of work here, it feels like I am wasting 3 precious years of my life.. I want to join one of the big 4 firms, so just wanted to enquire whether one of those 4 firms would even consider my application.. as I have started and completed 6 months of my articleship training at a medium firm? Do they consider transfers or do they take only those students who have passed IPCC in May 2013?

Plz do reply