Hi,
Having read this, the advice from CMK and Skywalker is completely wrong.
I am a property lawyer and would advise as follows:
1. If you pull out you will lose your 10% deposit
2.You are also liable for damages to the developer, the main one being if they subsequently sell the property at a lower price. You must make up the difference.
I would contact your solicitor immediately rather than seeking legal advice here.