Open Question: Should I give notice?

I am working as a freelancer on a UK contract (via an agency) in France. The manager of the department (ie the Client) met with me yesterday to tell me that they were ending my contract early because they had found a permanent person to take over. Since this meeting I have found out that maybe he is not telling the whole truth as the company would normally give me notice. What I found out is that he has been on the phone to stop my access to the company systems and is revoking my access to the building, so effectively I will be walked out of the building. What I am worried about is getting paid my notice as under the contract it states that I don't get paid notice if I have acted "unprofessionally" I think he is going to make up excuses saying that I have been unprofessional so as not to pay my notice. I have a meeting with him and my agency this afternoon and am told that it is up to my agency if I get paid my notice or not. Should I hand in my notice before this meeting so that maybe I will get paid my notice?