There is no getting around the fact that industrial action law is complicated. To get an injunction, you need to find technical faults in the union's strike ballot or in its correspondence…
Sometimes a negotiated settlement with a union proves impossible, and industrial action will be called. Industrial action can take many forms, ranging from working to rule (ie doing exactly what the contracts say, and nothing else), through to calling a strike.
Unions have legal protection from being sued if they comply with certain minimum requirements, including holding a ballot amongst the workforce.