Should you receive a message saying you can't access the forum / create an account due to the "IP address being blocked", then sadly there is not much we can do about this. We employ a service that is used to try and protect the forum from spam posts, which on the whole is quite successful.
However at times it does appear that certain domestic IP addresses can get blocked, this from experience tends to be some Sky Broadband IP addresses. We have looked into this issue, however we can't override the system. The best advice that we can give you is to try the site another day, as most IP addresses are dynamic so they will change on a daily basis. This we have found in the past is one solution to the problem.
We hope this is of some use to answering an issue that we get asked about.