Complex sentence: The BBC World Service broadcast from Bush House for 70 years (Winter 1941--Summer 2012); the final BBC broadcast from Bush House was the 12:00 BST English bulletin on 12 July 2012.
Split into simpler sentences: The BBC World Service broadcast from Bush House for 70 years, from Winter 1941 to Summer 2012. The final BBC broadcast from Bush House was the 12pm BST English bulletin on 12 July 2012.