SurferTim:
Many ISPs block port 80 requests from the internet to public ips that are not a commercial account. They normally want more money for this type account.
I haven't encountered that, and I'm not aware of any of the UK providers doing it. Some of them provide a firewall, but that's a completely different issue and you should have the means to configure the firewall policy to allow access to your server if you want. Usually it's enough to set up port forwarding within the home network and register the address with a dynamic DNS service.