Have you contacted the management company directors to clarify if everything is ready for handing over to the Co.Co. The Co Co could many years to take over the estate even where everything is done. Are the obvious things done such a roads finished, lighting working, checking with a few of the residents if there are any problems with water and sewerage. I assume you have been shown evidence that the Council will take over the estate at some stage. I would double check about the current validity of the Bond. Can you get the name of the company that actually developed the estate and you can check if they are still in business with the companies record office on line