WoL packets are sent to the network broadcast address, they don't need DDNS. The broadcast address is the "all ones" host address. For most home routers that'll be he one ending 255
e.g. 192.168.1..255 or 192.168.0.255
This ends up translating to the broadcast MAC address (all Fs)
The Magic packet format is essentially 6 bytes of FF ad then the MAC address of he device you want to wake up.
If a device is set to WoL it checks to see if the MAC address of the packet matches, if it doesn't the packet is dropped, if it does then the device starts up.
Note that you can't send a WoL packet direct to a computers IP address, because it doesn't have one until the operating system has started up, so setting a static address on your PC would not work.
Tim
Edit, if you're thinking of using WoL from outside the home network, it won't work unless you can connect to a device within the network that's able to send the WoL packets for you. You can't use port forwarding to send a WoL packet to the broadcast IP - this is a limitation on all SoHO routers and not just Virgin's hub.