Personally I wouldn't bother with a breach of contract action as what would that accomplish? Further poison the relationship to hang on to a job with a bunch of promise-breaking creeps? This question is largely opinion based, so all I can tell you is what I would do, not what you should do.
First, I would look around and make sure that the going market rate for my skills is at least equal to or above my current pay. If they are already paying me more than I can get elsewhere, then that will inform my next actions.
If it is possible to get equal pay or better elsewhere:
Then, I would have a sit down with my immediate supervisor (and the higher boss if he wants to come). I would bring my contract. I would keep my tone very neutral, not hostile or accusatory. My goal is simply to get final clarity on their plans -- whether they plan to honor the contract or not -- and to give them a final opportunity to do the right thing.
I would discuss my contract with them, and point out the clause where it says that I get a review (and raise) after a year of satisfactory work. Then I would ask what their plan is; if they intend to follow through on that clause. If he says "No, you're already at the cap of what we're willing to pay," then I would not make any threats about leaving or about bringing suit. I would thank them for their time, and say that I will plan accordingly. If they are smart and want to keep you, then they will read between those lines and possibly change course. If not, then at least you know what kind of people they are.
Next, I would start looking for a new job. In the meantime, no more unpaid extra effort for current job. I would not burn any bridges, and still give my best effort during my contractually obligated 40 hours, but that's all they get. If they ask me to do something on the weekend, I would say, "sorry, I'm busy."
Finally, I would accept the first promising offer that came along with a suitable compensation and convenient location. I would not hold out for a major raise. These people have demonstrated that they do not honor their commitments, and I would be anxious to move on.