Macbook Pro black screen - no power?

I have an Early 2011 Macbook Pro 13 inch, and currently having issues with the screen/internal display.

When I boot, the Macbook makes all the right noises, but the screen (and apple icon on the reverse) are completely off. I am able to work using an external display, but there is nothing on the internal display at all (in system preferences it only recognises the external display).

I have tried:
-Resetting PRAM

-Resetting SMC
-Using apple hardware test (showed no errors)
-Updating OSX

I'm thinking this looks like a hardware issue- are there any other things I can try or possible solutions? Or even anything I can test to make sure it is in fact the screen that isn't working?

I'm not sure if it's relevant, but the macbook seems to be in constant clamshell mode (i.e. if I close the display, the unit is still on. Even without the external display attached (with nothing displaying on internal display), closing the lid does not seem to put it to sleep.

Any help much appreciated!