I've done a rather extensive website for a client within the real estate industry. It consists of lots of work on my part, they paid the 10% upfront. A contract was signed, by Friday 9th November it was completed by. Of which it was. They have said they are paying me from other money they are getting from a development sale, and it could be around 2 weeks - I don't have "around 2 weeks" I need the money now. As a result of a signed contract, what is my best plan of action?