My understanding is that if they are on UC then HB stops immediately and they will get UCHC. If they are not on UC then they could remain on HB unless there were other changes that meant they must move to UC. Regarding the amount to pay this would depend on the landlord (If a registered provider then full eligible rent unless rent considered unreasonably high that you would refer to rent officer which would likely bring subsidy penalty) if registered charity or NFP then LHA or ROD.
