They were residing in Amsterdam but he dumped the body in Rotterdam and that was made fully clear in two episodes. It was not a mistake in the scripts.
Based on a true crime story. The bodies were dumped in canals in Rotterdam (not Amsterdam) and London.
Based on real events
The latest offering from writer and director Nick Stevens who has developed a specialism writing about real life serial killers.
As portrayed in this drama, based on the memoir by the victim, Delia with her problems dealing with others socially, her blunt honesty, her generally flat affect, and her unpredictable emotional reactions, especially to changes in the routines of her life, appears to be on the autism spectrum.