New tenancy

Letting Agents

On the 17 th of February 2020, my letting agent found me new tenants to move in on the 4th of April.
All references and other documents were done and new tenants expected to move in in 4 days time. Inventory check in was booked as well.
Today the agent emailed me saying that the tenants want to move in on the 4th of June instead, because B. Johnson had said no one to move unless necessary.
So I offered them to pay 80 % of the rent for two months starting 4th of April. . But they do not want to pay even 80% because they say the house will be empty.
Then I asked the agent how about the tenancy agreement.
She said that the tenants have never signed the agreement. I asked the agent why did she not tell me all this time that there is no agreement signed. She never replied.
I would like to ask what rights do I have in this situation as a landlord, please?