Welcome C21C to the British Airways board on Flyertalk. It's great to see you here, though I'm sorry to see the circumstances behind your first question. Please continue to post in this forum, hopefully some of your future experiences will be more positive. Welcome on board.

My experience is that BA will pay a higher taxi fare if the circumstances are fully explained. I presume you are saving BA a hotel bill, so I suspect your claim will be somewhat lower than many other people stuck that night. £75 seems a bit high to me too, but the East End does go on a bit I guess. One relatively quick and easy thing to do is to call BA and ask them to pay the taxi charge in full. Alternatively - but this will drag the process out for longer - send it a customer service webform via the Contact Us section of your BAEC login.