Looking at the picture of my v8 when it was still in the car, I think with the radiator removed, you'll have enough space to work with. You need enough space for a drill. The water pump needs to be removed of course. So is the throttle body. You may want to also remove the flex damper.
Go to Home Depot to get yourself a set of Cobalt drill bits. The trade name is Blue Mol. These drill bits go through steel like butter. But you need to be careful because the aluminum block is actually softer than the stuck bolt. The Cobalt bits are also quite brittle being so hard.
Use a center punch (the smallest size finished nail punch) to punch an indentation right in the center of the broken shank so you can start your first drill bit centered. Start with the smallest drill bit to drill into the shank. Don't go deeper than the broken shank. You don't want to drill into the block. Increase the drill bit size one at a time until you reach the maximum bit size required by the proper size bolt extractor. Then use the bolt extractor to get the shank out.
'01 540it, 6/01
'03 325i 5 speed, 9/02
'10 535ix. 9/09
'10 mini 6 speed
'15 mini countryman 6 speed