Soldato
or leave and then they would be out of pocket anyway?
Nice way to treat your friends there. They've clearly done the OP a favour by not being turds about the contract and lack of formal recognition for this person. They have potentially all jeopardised themselves by allowing the OP in with no contract which = subletting = illegal.
It does all depend on the contract and how long is left to run thereon. If this is renewal stage then leaving would be absolutely fine. Just packing up one day and leaving them with two empty rooms and with all of the onus to fill them is unfair. Telling them that you will be leaving in advance etc is fine.