Terminating contract at creche (Urgent advice needed)

I am trying to cancel the contract I have for my daughters creche before its stated "expiry" date...

We have originally agreed, not in written form but via email, that our daughter would leave creche end of August. However, as we will leave for holidays in July, we wanted to terminate the contract earlier.

To do this, I initially wrote to the owner of the creche 3 months in advance, thinking this is the legal requirement. I did however not check the contract at this point.

After this, we did not get a response, until just a few days ago (after sending her a reminder). We have now been told that we will loose the deposit if we take her out from creche before the agreed end of the contract (so end of August). Despite having given her 3 months notification.

So, my question boils down to this. After having finally read the fineprint. The contract states that I will loose my deposit (even if i give 3 months notification) before the agreed end date, the only benefit of giving a notification is that I would not get any additional penalties.

For me, this sounds very strange, and I wanted to inquire if anyone knows the legal requirements for breaking a contract? Certainly I should be able to break any contract if I give enough notice?

Any help on my legal position would be greatly appreciated!