Hello guys.

I recently got a SIIG DP FW800 card and can't get it to recognise on the mobo (mobo boot up is not giving me the hardware change beeps/is not recognised when installing drivers on Windows 10)

Anyone have any idea? Am not using PCIe slot (small one) because of my M.2 drive.

Sadly support for FW standard on W10 is seriously lacking. Some got it to work, others not. I don't know even if it has official support from M$.
 
Have you tried for example this:
 
https://blogs.msdn.microsoft.com/usbcoreblog/2014/09/10/announcing-the-availability-of-a-standalone-legacy-1394-ohci-firewire-package/
 
As for motherboard not detecting the card. I know the pain, believe me with much more expensive piece of hardware than FW controller. Well if old trick of setting slot to Gen1 mode doesn't work then it's end of story - outside hoping for UEFI fix which considering FW is nearly dead standard is rather not high on priority list (send Jacob PM). Every UEFI is different, every board reserves different areas for hardware detection. Card which work on one board may not work on all other competitors. Fantastic thing isn't it, that UEFI Progress... I will not stop rambling about it, because UEFI is [* * * * * * * * * * - put in here some colorful expletive :P]. Period.