Series 3 XKE throttle cable stuck

Looking for some help so I am writing my first post. Series 3 1974 XKE with sudden onset of gas peddle not depressing. Pedal is fine but throttle cable is stuck. Used cable lube to the point it would come out in foot well bu cable will not slide.

I have a replacement but can’t access the nut holding the cable to the firewall. Any suggestions on replacing this cable and reaching this nut?

Thanks
Chris

Best is to loosen the nut on the other side inside the footwell, that nut has to come off anyway to get the cable out and up thru eng compartment side anyway.