Acces to bmw 316ise x regd boot

it sounds like you can get into the front of the vehicle. you can back feed power through the cigarette lighter in the vehicle. Also you can pop the hood and connect jumper wires to the jump start points underneath the hood. You could also apply power to the fuse box and ground to chassis. the easiest would be using the cigarette lighter (just don't turn on the vehicle to the point where there are a lot of loads going through the cigarette lighter or you'll pop the fuse)