One of the first things I needed to check before ordering my Raspberry Pi was if it was technically feasable to host my own webserver from my Sky Broadband. In the past its been known by ISPs to block certain ports which makes it difficult and usually adds extra cost.
One of the ways round the issue of your desired ports are blocked would be to use some sort of service which relays incoming port 80 traffic to another port to your server. Its messy and is probably going to cost for this service and given one of the reasons why I've got a RPi was to have practically free hosting.
It seems there is no information on the internet as to whether Sky blocks port 80 for their broadband users. I'll cut to the chase if you can be bothered to read the rest of the article to say that:
Now we have established this, its just a case of setting up your router to forward internet traffic to your Pi webserver. There's a helpful page on Sky's support website explaining how to do this:
Sky Hub : How to Configure Port Forwarding
Well thats the easy part, next you've got to get around that whole dynamic DNS thing, but luckily for you I've got a tutorial for that:
Setting up your own domain name with a dynamic IP address on Sky Broadband