I though you said you were moving to Sky?
Because of the large number of proxy sites, its not possible to block them all, unless you add each one to the blocked list on BT Parental controls.
The same goes for VPNs.
The only way would be to only add the sites you want to allow to a "whitelist", and block everything else.
You would have to keep adding to this whitelist, but you would have full control.
Every other category would have to be blocked.
I decided to stay because the controls came back online and finaly worked.
Why doesnt BT have a blocked word like my router has ie "proxy" setting? that would work