Ultimately, if it is skilled workers that are not easy to replace that are taking industrial action, the law becomes almost irrelevant. If the company dismisses employees, they will be short staffed and will further anger those that remain. Thus there is likely to be more industrial action. And it will be increasingly difficult for the company to run a normal service on non-strike days, let alone run any kind of sensible service on strike days.
Further, if the staff levels fall, then unofficial action could be taken. No law can protect against a sudden unofficial walkout.
Remember, in our past, taking any industrial action was illegal.