Hi Mr.Woflcaw, I haven't used Hyper-V since 2012R2 (IIRC) but remember having issues with either internal only or host only networks. My solution was to install a firewall like Open-WRT, DD-WRT, or pfSense and use rules to control connections. Its a little awkward to setup, but gives you alot of control. I still use this process now in Unraid, a pfsense VM with both Real and Virtual NICs.
Thanks for replying. I had some progress, setting the virtual nic on the server to 172.x.x.1/255.255.255.0, enabling internet sharing on the physical nic, set the VM nic to 172.x.x.2/255.255.255.0/172.x.x.1 and disabling firewall on server and VM, I got connection and could browse internet from VM. Don't ask me what firewall rules I would then need to set after that