Is this legal?

Today 28/05/26 I have received a message from my landlord (Call her A) stating the following:

"Hi, please note that the landlord requires possession of the property due to them wanting to sell the house, you will receive notice and documents in the post in the next few days.

Not sure if you would be interested in buying the property but please feel free to discuss further if you do."

This was quite confusing, because I thought A was my landlord.

Once I got home, I found an unstamped letter in my post box.

This was notice that my landlord has changed from A to (let's call them B)

The letter states that B is my landlord effective from 1st May 2026.

This seems incredibly suspicious to me. I have found out I have a new landlord on the very same day I am informed the property is going to be sold. The letter itself has clearly been posted today.

I haven't received any other official documents as of yet.

Any insight would be a massive help.