So it seems that the internal Virtual switch with a bridge across the Wi-Fi works. However... It seems that with the XPS 12 after waking the laptop up from it's slumber (sleep) the Network connection doesn't renew sometimes. Therefore occasionally have to bring up the old DOS window to refresh the DHCP info > ipconfig /release > ipconfig /renew .
Also found out that removing a Virtual Switch which a VM relies on whilst it is saved is bad. Had to create a new one with the same name as the old to load it again!