Digging around, whilst ssh restarting apach, I get:
[Mon Dec 08 12:19:14 2014] [warn] NameVirtualHost x.x.x.x.:80 has no VirtualHosts
[Mon Dec 08 12:19:14 2014] [warn] NameVirtualHost x.x.x.x.:443 has no VirtualHosts
Which is the new IP of the server.
This error also appears for the old IP’s, which I though I scrubbed!
In addition to changing the IP address in your network interface, you’d also need to update your various config files with the new IP address.
To do that, go into Addresses and Networking -> Change IP Addresses. There, you can update all the IP’s at once, which should get your websites running again.