The burden put on network infrastructures is changing. The increasing number of connected devices, along with growing demand, are creating an unsustainable future for the Internet. The recently introduced concept of Fog computing predicts a future Internet where general compute power is ubiquitous, extending the Cloud right the way to the network edge. In turn, this acts as a catalyst for Network Functions Virtualisation (NFV), increasing the potential infrastructure locations for deploying new services, specifically ones that can cater to the demands of the changing Internet. However, current realisations of NFV typically host network functions in homogeneous, centralised servers in Cloud infrastructures. This is in contrast to the Fog where environments are both distributed and heterogeneous, thus current management and orchestration platforms suffer from suboptimal service deployment. With the use of a multiple use cases, and a novel auctioning orchestration method, this paper presents Siren, which is an orchestrator for network functions in the Cloud to Fog continuum.