I would think about getting in touch with watchdog you maybe able to get some free independent advice! Also you would think that the ground would have some sort of water table survey done in the planning process for development of the site. Things like roads and street lighting responsibility can be automatically taken over by local authorities after say 12 months you need to find out if its the same for drainage? I just tried some searching online and you can contact ombudsmen http://www.lgo.org.uk/publications/f...bout-flooding/ Hope you find a solution