unable to access VM

[john_in_wales]

Hi,
I have a problem with not being able to access VM's on a Ubuntu server host.
I have several VM's (Ubuntu 14.04 guest), which all work fine on a Windows host, and on a Ubuntu 14.04 Desktop host, with both host-only and bridged network adapters.
However, I am now trying to set them up on server with Ubuntu 16 server, i.e. no no GUI and only remote console access.
I have set up the VirtualBox host and extensions, and also installed phpVirtualbox. I have imported the VM's, and they appear to boot, but I cannot access them with a host-only adapter. I can't ping the guest, or ssh in. The phpvirtualbox 'remote console' doesn't connect.
Starting them with phpvirtualbox, the 'preview' shows the normal boot info, and the corrrect hostname and login prompt, so I am reasonably happy they boot ok, but this is only a 'screenshot' not a console like you get with the windows or Ubuntu desktop client. So, with no 'direct' console, I can't log in to see what the guest is doing and what ip it has recieved. I have tried setting the dhcp server to a very restricted address range (dhcp server as 192.168.56.1, range 56.1 - 56.5). Only 56.1 gets any ping response, but is just looping back to the server.

So, any ideas what is going wrong with the network setup that means I can't see the VM? How can I get access to the VM if I can't use a remote terminal?
Let me know what diagnostic info would be helpful...

Thanks in advance.