Site blocking

[#1]

Why is it that I can't access certain websites through my PlusNet account. These are not illegal sites so why is PlusNet blocking them. If I use a vpn I can access them no problem but PlusNet must be blocking because I am unable to access them. Is there a list of the sites PlusNet blocks and what is the policy on such censorship ?  
adie:red all caps subject removed as per link:rules]

[#2]

What sites are you trying to connect to ?
Have you tried a different DNS server ?

[#3]

PN subscribes to the IWF list which isn't published for blocking child abuse sites and there seems to be some blocking if your traffic is routed through BT for P2P.
What sites are you talking about?