BMW Repair Questions? Ask a Mechanic for Answers ASAP
turn the key as far as possible, it should open manually
if not, try applying jumper power from under the bonnet and see if the car will power up
if not, you will need to have the car towed so some of the interior can be stripped and power applied directly to the boot release wires
Please let me know if you have further questions. Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you. Best wishes with your vehicle.
Applied jumper from under bonnet and managed to open boot.