Trying to replace oil cooler?

Hi there, I'm trying to change the oil cooler but in order to remove it, I need to take out the EGR crossover pipe and there are two bolts holding this one. i have surprisingly managed to remove it but the second has before me been rounded off and it's impossible to fit any spanner or mole grips adjustable in there as the bolt is on the opposite side to you and there is no space for a drill on the front side. How do i get this stubborn bolt to move? Thanks in advance, William Sharp