Help needed

Access

I was just wanting a few views on my situation

my tenants rent date is on the 2nd of each month and they handed there notice in on the 13th so it says in the AST that it has to be on a rent date when you have to accept the notice so really if they hand there notice in on the 13/08/09 then i can't really accept this notice till the 2/09/09 to end on the 01/10/09,

My tenants seem to think this is so unfair so do you think i'm doing the right thing and making them stay until 01/10/09 as i told them i dont have anyone to move in until the 01/10/09

I would appreciate any advise