My laptop screen has stopped working and I've tried the following:

Checked the cabling, all is ok.
It lights up white sometimes so the backight still works. (does this mean the LCD isn't broke either as I can get it to light up.)
I changed the inverter, still no joy.
If I use an external HDMI connector it works fine so can't be the GPU

So if it's not the screen, backlight, inverter, wiring or GPU, why won't it work?

I don't wanna risk just buying an LCD and replacing it as if its not that its a waste of £70.

The laptop in question is a HP Pavillion DV5-1015ea, they DO have inherant graphics problems but my symptoms don't seem to adhere to the normal ones most people get.

The back-light and the LCD matrix are two different components. If it was the inverter it wouldn't even light up.

As you say the face the HDMI works proves it's not a GPU problem.

If you're 100% the cabling is OK it's time to bite the bullet and buy a screen. I would buy it from a reputable seller on ebay.

Is there a DVI / VGA port too? if so I'd test them just to be sure.

Has the screen output been switched from internal to external then, you mention that external works, some laptops you have to press ALT F key combinations to get them to switch the screen back on. Look for screen like symbols by the F keys.

No is a windows 7 machine, pressing (windows key) + P allows you to change between laptop screen / extended display / duplicate display / external display only. I know its deffinately not a software setting.

I removed the shrink wrap to check the cabling for shorts or loose socket connections and its all fine. The built in web camera on top of the screen still works and thats powered by the inverter from what I can tell so all that leaves is the screen. I'll see how cheap I can find one.

I may even take it to one of these, no fix no fee, repair places, might work out a little more expensive but at least there is less risk.