@Dando83 Unfortunately, your ideal setup, as mentioned at the end, is impossible. You would be best advised to wire an unmanaged switch after the M4 to give you the required ethernet ports for your...

@Billy_Ladd If you disconnect the M4, are you now able to connect the iMac to the outside world with the ethernet connection? If so, there is no problem with the VirginHub and the issue must be...