E1-571 not posting, any ideas?

So, I've had this laptop for 2 years now, it is an E1-571-33114G50Mnks it has always worked really nicely, I upgraded the ram to a kit of 2x8gb sticks and that also worked fine, shortly after it upgraded itself to win10 the laptop would take ages to post, we're talking 20mins, but sometimes it would be instant! recently it will not post at all, I hit power and blue lights come on, specifically the power LED and HDD read LED and oddly, regardless of wether the AC charger is connected or not, the battery charge indicator flashes a slow orange, (NB. after tearing down the whole thing, re-seating everything and re-applying thermal grease, the orange light now behaves correctly) if it is left to run for long enough it will at random each time beep at me, a single beep every ten seconds. Now I haven't just jumped on a forum begging for everybody to use google for me, I have seen, tried and failed with many many solutions.

I have (Updated to save pointless reading below):

1. Held down the power button for 30secs, then 60secs, then 120secs with no power source inserted 
2. Held down the power button and F12 for 60secs with no power source inserted
3. Pulled out the battery whilst powered on and re-inserted
4. Removed HDD and powered on
5. Removed/swapped memory slots and powered on in all configurations
6. Removed, cleared and re-inserted the CMOS battery
7. Powered on, pressed F2 then F9 then F10 then return and rebooted
8. Powered on hit all of the above keys simultaneously and then rebooted
9. Plugged in a second monitor to the HDMI slot then pressed all 'F' keys to try and switch monitor 
10. Held a torch to the screen to check if the backlight is dead
11. Powered on with the screen at various inconvenient angles
12. Accessing BIOS by mashing F2
13. Using BIOS crisis' Fn+Esc with a usb BIOS inserted resulting in 3 beeps then a power-off
14. Replacing the CMOS battery
15. Disconnecting all non-essential strip-cables to the mainboard and powering on

All to no avail whatsoever.

(Obsolete text, IronFly has graciously helped explain some things however so I'll leave it in for context) 

What I want to try next is the crisis BIOS flash using the supposed Fn + Esc immediatly after power-on but the BIOS files are windows applications and not the usual BIOS files I am used to when performing these sorts of Reflashes, is there anyone with any ideas, I will eat them up, I really don't wanna accept that it's cold solder or a fried GPU

Thanks to anyone who even bothered to read this, really.