Complex sentence: Production Sea Vixens were first built by de Havilland at the former World War II Airspeed Ltd.'shadow factory' at Christchurch near Bournemouth from March 1957 to August 1962 when production was transferred to another de Havilland factory at Hawarden, near Chester.
Split into simpler sentences: Production Sea Vixens were initially manufactured by de Havilland at the former Second World War Airspeed Ltd.'shadow factory' at Christchurch near Bournemouth, starting in March 1957. In August 1962, all production activity was transferred to another de Havilland factory located at Hawarden, near Chester.