Diff fluid change??

I tried to change the diff fuid on my 94 325i, but I can't get to the bolts on the rear end. The bolts are 14mm hex bolts. The allen keys that I was using were too long and didn't fit in between the rear end and gas tank.

What kind of allen keys do you guys use to change your diff fluid?

Mac, have you got an angle grinder, or a decent hacksaw?

Stephen