I plan to use Hikvision DS-7608NI-K2/8P - 8 Channel NVR POE this has 8 Ports Ethernet POE ports
is it possible to use 1 port of the NVR and connect a cable to a switch in the loft to run to 5 cameras off the single port ?
Yes, some settings have to be adjusted in the NVR but it is possible to connect a switch to the PoE ports on the NVR, but the switch cannot exceed the max. number of cameras that the NVR supports. The video below explains how to do it: