Hey barryd999,
I believe there's no plans to get parental controls added to the BT Business services. The reason behind this is because that's mostly used for parents with kids and businesses would rarely need the service restricted, but I do understand the reasoning in this instance. You would probably be best speaking with the BT Enhanced IT Support Team on telephone number 0800 500 247 who may be able to offer another solution - that line is chargeable for any help that they provide, but you'll be notified of this before carrying on. They will be able to help with third-party setup including Open DNS on the BT network.
Thanks, Bobby