Thanks for your question.
Some times a property will be put with multiple agencies. Maybe the landlord or the agent who let the flat to you did not tell the other agent.
I can sympathise with your position considering your recent diagnosis.
However to sue someone you need to have suffered loss or detriment.
I cannot see what you can sue for.
You can explain the situation to the agent/landlord and ask for confirmation that the situation will not happen again. You could request a security lock be installed which you can lock when at home so nobody can enter when you are home with the security lock on.
I hope this helps.
Any queries please message me.
Please can I ask you to accept /positive rate my reply.
I am just following up. Can I help you further.
Going forward do know that your landlord or the agent myst give you at least 24 hours notice if it wants to enter unless it is an emergency.
Dany further questions regarding this?