MacBook pro grey screen loop

Hi,

I updated my MacBook Pro 8,2 today to High Sierra.

It updated successfully then about an hour after the laptop crashed. Upon restarting it displayed the apple logo then a grey screen the reboots and loops doing the same.

So far i've tried:

PRAM reset. cmd+alt+p+r (three times)

SMU reset. shift+ctrl+alt

Hard Drive First Aid in my other mac.

Verbose boot completes then back to grey screen and loop.

single user mode boots then run (fsck -fa) shows as hard drive OK.

Also does the same when booting into recovery(cmd+r) and internet recovery(cmd+alt+r) also same from usb installer.

I'm at a complete loss. Could anyone help please??

Thanks, Jordan