I paid for my tickets through BA. I flew BA. I made the assistance request with BA not with Heathrow. BA have at
least a duty of care to ensure this request is met, not to say 'not my fault mate blame HAL' as you are clearly doing. You are just showing again that BA and some of their staff really don't give a toss. Can I not help you would be more appropriate.

(If the assistance request was made separately to the airport by the customer and confirmed directly by the airport back to the customer, then obviously things would be different).