I jiggled with the cables for both monitor and PC. No luck.
So I opened her up, less blue LED light than usual on the graphics card. Tried reseating it, jiggled the PCI-E power connectors (2x 6 pin), no difference. The graphics card fans power up, and eventually after it POSTs (I assume, because I can't see anything) it seems some of the graphics cards blue LEDs are getting power but not all. Usually I can tell it's working fine by the blinding blue light.
So I'm on integrated graphics now.
I'm gonna try a couple of things. Different output (maybe its a RAMDAC?) if I can find a HDMI or DP cable, different VGA power cables, then I'll try taking the heatsink off, cleaning and reapplying thermal paste. Can anyone think of anything else to try? It could possibly also be the motherboards PCI-E slot but my gut tells me it isn't because it's newer than the graphics card by a couple of years and my PCI-E wifi card is working fine. I assume I can test that by putting the graphics card in a lower slot even though it isn't 16x?
It's a MSI GeForce GTX 670 OC PE 2GB, and I've had it for... almost 4 years so it's well past it's warranty. If it is truly dead it's a shame because it still plays all my games pretty well.

If I do have to replace it, it seems I'm a month early for the GTX 1070 and I don't think I can survive that long, but considering the rumoured prices it would seem silly to pay £200+ for a GTX 970? Or to stay at the same level, I guess the GTX 960 won't be replaced for a while yet? I'm wary of going to AMD because one of the games I play - FSX - works better on Nvidia. For reference, I play at 1080p and that's unlikely to change soon so perhaps I should just stick to my usual budget of <£200.