I am so sorry this happened to you @Pedro851 what an awful experience. While it is highly unusual for this to happen out of the millions of bookings that take place through Airbnb. Unfortunately there are some unscrupulous hosts out there (seems to be more prevalent amongst multiple property owners or property management companies to do click and bait).
What was communication like with the host prior to your check in? What were their previous reviews like.
In general if you book with a long established superhost with lots of recent positive reviews, you are much less likely to have a bad experience.
I am sorry that Airbnb did not respond to you more quickly to help you find an alternative Airbnb or help you secure hotel accommodation. Do make sure they cover your taxi and food bill from last night as well as the hotel cost.
The good news is that it is low season in London at the moment so hopefully it won't be too difficult for Airbnb to find you suitable alternative accommodation.