The only way you can get a company on its knees is the threat of very bad advertisement. If you tell them you are going to the big papers more than likely they will change their mind.
But you have to follow up on the threat and do it....they will wait till the last moment to change their mind but i think they will.
Big companies have got very good relations with Developers. The big property companies can get your money back because of all the business they have given this developer in the past. Trust me!