Inspiron 7520 15R SE - Purple screen upon upgrade replacement?

Hi all,

I accidentally broke the screen on my partners Inspiron 7520 15R SE laptop. I managed to close the lid when there was a dongle on the keyboard... DOH!

The original screen as "WXGA (1366x768) HD" but I decided that as an apology, not only would I replace the sreen but I would upgrade it to the "WUXGA (1920x1080) Full HD" model.  I purchased this from a reputable company and fit it myself (I like to rebuild M1730's in my spare time... great machines... so I tend to know what I am doing).

Unfortunately, the screen has a strong PURPLE tint to it, even in POST/BIOS and this purple tint stays even when the machine loads in to windows. The purple is persistent and never changes or leaves.

I read somewhere online that it is possibly the LCD cable and so I purchased the R4WW7 cable and replaced that. The purple screen is still there. While this picture isnt great, as the purple looks gradated, I can assure you that it is entirely uniform in it's purpleness. http://postimg.org/image/kdlez6rkp/

So... What can I try next? Is this a screen issue (so therefore should I ask for a replacement/refund) or do I need to look at maybe another issue on the laptop?

The machine is:
Intel(R) Core(TM) i5-3210M CPU @ 2.50GHz
AMD Radeon HD 7700M Series / Intel(R) HD Graphics 4000

Thanks for your help.