Ballooning is a common activity in the Bristol area. The controllers that can provide services in the area are experienced in the handling of balloon flight, even those that are a little unusual. The reports aid that the pilots were in contact with Bristol ATC. In this case I imagine that ATC was simply providing a FIS to the balloon whilst it was largely in class G airspace - I would hazard a guess that it was co-ordinated with other appropriate agencies such as the mil. If it was necessary for the balloon to enter class C airspace (as described by NoD) I can see no difficulty in the controller at Bristol co-ordinating a suitable clearance. A slightly unusual flight but nothing to challenge controllers, especially those with experience providing services outside CAS.