I'd talk to the cops. As Sorcha said, they may be able to offer some assistance before, during, and after the move. They may also have some very good advice on how to handle the situation.

If it were me, I'd ask the friend I'm moving in with if I could move in as soon as I told my flatmates. I'd ask my friends if they could be there for support and to help me move my stuff out of the house right before/during/after I'd told the guys. I would not give them a chance to plan anything. The official notice means you'll still pay rent for a bit, but you don't have to be physically present.