Good recommendation from handyman with vnc, you have more configurability with what port you you need your vnc server running on. If your only going to use MS RDP, then you need to port forward port 3389. If you have all MS OS's such as XP Pro or 2k3 server, you can RDP from one to the other just using it's computer name and don't see any slow down really.
Go to dyndns.org as Stuart C says and signup with them. Create a static account and enter the username and pass in to the
https://192.168.1.1/DDNS.asp page (your IP address maybe different). If you want to use your .co.uk domain name, you can create a CNAME record and point it at the domain name you have created with dyndns.
Might be a bit pointless, but fun all the same!!