Current approaches for the provision of autonomous team behaviour assume that team members are able to communicate with each other whenever they wish. This is an assumption that does not always apply in the UAV domain. Environmental conditions, such as weather or terrain can invalidate this assumption, as can damage to the UAV itself. Also mission requirements may mandate that there are periods when no communication is to occur. The potential inability to communicate within the team at critical times leads to a reconsideration of the underlying team architecture and of the way in which behaviours are modelled and executed. It also emphasizes the need for the ability to dynamically reassign roles within the team when required. In this paper, we present a conceptual model to underpin the provision of robust team behaviour in the presence of such perturbations. The conceptual model extends an existing teams infrastructure (JACKTM Teams), which in turn is based on the BDI model of agency.