Here is the response I received:
"To follow-up on our conversation earlier, we encourage all hosts to host responsibly and comply with local regulations. We sent this email to you and other hosts who are approaching or have reached 90 days of hosting this calendar year.
Only hosts who have listed an entire home in London on Airbnb will be limited to accept bookings for 90 nights per calendar year. Private rooms are not affected by these automated limits in London. You can simply ignore the email if this doesn't apply to you.
Here are some helpful resources about responsible hosting in the United Kingdom:
https://www.airbnb.co.uk/help/article/1379/responsible-hosting-in-the-united-kingdom
https://www.airbnb.co.uk/help/article/1628/night-limits--frequently-asked-questions
Please let me know whether I can still be of help; otherwise we'll close out this issue for the time being."
While I appreciate the fast response to my query, I don't think Airbnb should send hosts random emails telling them their booking is going to be blocked when this is not the case. The email I received this morning said:
"On March 1st 2017, your calendar for the listing will automatically be blocked for the remainder of the year and you will not be able to accept further bookings for the rest of the year."
If I had taken the email at face value, rather than questioning it, I would be removing my listings from Airbnb ASAP!!