Connect system draining battery

[KirstyK]

Our connect system has been draining the battery - resulting in numerous calls to the RAC! An independent garage has diagnosed the issue as the radio amp and taken the fuse out. It's cured the battery drain problem. However, Nissan Shepperton say that it can't be mended and we need to replace the whole connect system at a cost of about £1600. Has anyone else had this issue or can advise? Thanks