Tenants Pulling a fast one?

Other

I'm new to the forum and also to being a landlord but already have a query.
I'm about to let a 5 bed house to 4 tenants, starting from the 1st of September. Orginally the group was 5 but I got a call last night from one tenant informing me that her friend wouldn't be signing as her father had died and her head was a mess. I enquired about the nature of the death and how her friend was out of genuine concern but she didn't have a clue and i got the distinct impression I was beng lied too. I said that it was OK, I understood and would rent to the 4 of them, but would look to rent the 5th room out. This drew a startled response and the call was cut short. i then got a call back to say the 4 would only rent on the basis the 5th room was left empty. Given the timescales before the student year, i really need to give the property over to the 4 as there is the chance it could stand empty, but feel that the prospective tenants will allow a friend to move into the 5th room.

I am going to sign these tenats to seperate agreements, am I within my rights after they have signed their contracts (I'm getting parental gurantors)to lock the 5th bedroom for the duration of the tenancy or use it to store furniture for from my own home? I'm concious of being duped over the matter and would like some advice over what to do.

Thanks

Chris