If you paid with a credit card, your card provider is responsible for refunding you, get in touch with them immediately - you'll need to provide evidence, i.e reciepts if you still have them.
If you didn't pay by credit card I'm afraid there's every likelyhood that you've lost the lot.
It's no comfort to you, but this is yet another timely reminder that no one should pay up front for "block hours", no matter how attractive the deal may appear to be at the time, organisations who offer this facility are often scratching the surface to survive and usually cannot be relied upon.