when using a dynamic IP you should use a dynamic DNS service to ensure that you can connect independatly from knowing your IP-address (there are a lot of them out in the wild: no-ip, dyndns, …)
Next steps are very dependant on how you want to use your MBWE…. If either of you two (your dad and you) use "any" computer (i.e.: internt cafe hardware) or specific ones (i.e.: your computers, laptop when abroad). If the latter is the case I suggest to use a VPN software for connecting your drive. As you already have the optware package in place, there is a tutorial on deploying OpenVPN on this site. When you connect to your MBWE based on its home-IP (i.e.: \\192.168.x.y\public) rather than on it's netbios name (i.e.: \\myMWBE\public) your drives will be available everywhere… THis will keep you seperated networks on the WAN and LAN side which is a security plus for the solution. You should generate client certificates for each of the computers you plan to use from "abroad" your home network.
FTP can also be a valid solution, but you will experience a different "look and feel" - and everybody can reach your MBWE using FTP and knowing username/password pairs on your MBWE.
In both cases you will have to enable port forwarding on your router. I assume that the Belkin is capable of doing this, but can't check as I don't know the modell involved. I have to say that I don't know if your Virgin/NTL assigns you a public IP - if not we are in deep sh… - but I assume they do.
So here are the steps:
1.- check which dyndns service is supported by your router
2.- go for a symbolic dynDNS or no-ip or … address
3.- configure your router for the use of the service
4.- decide on using
4.a.- FTP or
If you opt for 4.a.
5.- configure port forwarding for FTP (generally port 21, TCP) to your MBWE on your router
6.- go for it - you are ready
If you opt for 4.b.
5.- install openVPN via optware as described in the tutorial on this site
6.- install openVPN client on the computers you need it
7.- copy appropriate certificates and keys to your clients
8.- go for it - you may use the MBWE abroad and at home in the same manner…
Ask if there are open points…