Thank you for the link Brian. That was quite useful. I have decided to go down the route of installing using a DR file. When I download the installers, there are three files.
Symantec_Endpoint_Protection_12.1.5_Part1_Installation_EN.exe
Symantec_Endpoint_Protection_12.1.5_Part2_Tools_EN.exe
And
Symantec_Endpoint_Protection_12.1.5_SEPM_EN.exe
Which files do I need to install onto the new server?