That shows 13.9Mb for my connection, while my Billion and Routerstats show a 16.059 connection. Can only be PN!
What's your BT IP profile? If you're synced at 16059k, your IP profile should be 14164k, which is not a million miles away from Plusnet's 13.9Mb. In fact I'm not convinced that Plusnet don't use "binary" megabytes, in which case it's pretty much identical. Either way, I don't see the problem.
Kevin
plusnet Extra Fibre

Using
OpenDNS