Exactly, but you can tell someone it not BT until your dying day and they may still not believe you, if you can show them, or better still give them the information to see for themselves they are much more likely to understand.
For those of us that have setup different VPN servers and clients and understand how they work things can seem obvious, but for those who have been told - use this VPN then when it does not work they often point the blame in the wrong direction as they have no evidence of what is happening (or more likely not happening).
Hopefully the OP can now see that BT have no role in the VPN and are not actively blocking it as first suggested.
Using tracert will show that once the VPN is in place, any thing sent is not visible to BT as it has been encrypted by the VPN client and needs decrypting by the VPN server, BT only sees a packet of data going from one place (customer)to another (the VPN server host) and has no role in the encryption/decryption (the same applying to other ISPs).
Solving why one VPN works for the OP and one does not will require more digging.
Hopefully, when the next customer comes along with another similar VPN problem they can read this thread and see how to tell for themselves that the problem is not BT (or other ISP) and realise that not all VPN's are the same.
