reply to griff
You may have an alternative option as well. Without having to go through any such technical steps, you can also use a service called Log Me In (www.logmein.com) to be able to get access to your files and such on your systems at home from anywhere in the world.
Short of this, the other option that I can think of would be to use a DDNS client through a service such as Dyn (www.dyn.com) to assign a static host name to your IP address, which re-registers with the network every time that the connection changes. From there, you would be able to setup the port forwarding and such to be able to access services and such across your network from the internet using that host name.
Should you need any help configuring any such service, it just so happens that I own a small IT company that specializes in such things. I also happen to be a certified Microsoft technical support (Tier 3) rep, so if you're dealing with a Windows based system, I can be sure to get you on your way, regardless of the setup or configuration that you're trying to establish.