Unable to connect to company VPN

[#1]

Yes, same result.  Cannot connect to site.  Looks like I'm going to have to leave plusnet.

[#2]

Have you tried alternate DNS servers or a different router

[#3]

I have not tried different dns servers, I can try that later.  I have taken the router out of the equation by connecting straight to the fibre modem.

[#4]

In post #2 you said the firewall is set to standard, have you tried disabling it?
Have you looked at the link provided by avatastic in post #6. There's a workaround there to test if BT's modem is the problem.