Going on strike is a clear breach of contract and they can fire you for that,END OF. You would have no recourse. Oh,and going sick on a strike day will be considered as going on strike on a strike day,and therefore a sackable situation. The potential response to your action is unaffected by whether or not you hold union membership-VS have no idea which individuals are members and which are not.
You only have a legal right to strike,NOT a legal right to keep your job if-IF the company decide to fire you.Hasn't your union made that clear? If not,examine your legal position WITH THEM!