Is it now safe to assume that this next action will be unprotected? And will the union leadership advise its members accordingly?
IMHO, Yes I believe this action is unprotected which maybe why UNITE have not declared strike dates. On the previous occasions the union have been pretty quick to announce these dates. I know they have 7 days now to do this and I really hope they reconsider their position.
As for your second question they have a moral obligation to advise their members that their action would be unprotected but I think that they will sincerely believe the opposite and so they won't.