Outstanding S106 contributions being levied against potential flat owner? - Public forum - Planning Advisory Service (PAS)

I am trying to close on the purchase of a flat. The council have told us that the s106 contributions (roughly £48,000 total) on the property are outstanding/expired. There is concern that these would be levied against us, a prospective flat owner within the development. The s106 agreement was entered into by the developer in 2006. 

- How likely is it this could be enforced against us? Agreement was entered into in 2006.
- Would it not be split across the 18 flats in the development?
- Does the statute of limitations come into effect? We're trying to purchase this flat this year, and the agreement was made in 2006.