The problem is that the incremental cost to filtering additional material is now virtually zero. I'm not sure how this would play out in Britain, but I know many countries where a conservative government would have a field day expanding this list. It is easy for a politician to make the case that something should be blocked (think of the children!), but I am guessing no politician would stake his personal capital on unblocking something even remotely controversial. Unfortunately, now Britain has set a precedent, and I could easily see other governments in Europe pointing to Britain in justifying similar firewalls.
Therefore, I have concluded that we have a binary choice, firewall or no firewall. To me, this is a simple decision, I would not entrust any committee at all with the management of what should be considered obscene.