There is much said on these Forums about the speed, or lack of it, from PlusNet.
If you are concerned about your speed, as advised by PlusNet, the first step is to do the BT Speed Test. If that is slow, then raise a Ticked with PlusNet. If the speed is good then you have to check the PlusNet speed.
There are many speed testers, including their own. AdslGuide is another popular one. But none of the Internet speed tests are much good. A better and more accurate test is to upload a file to your webspace. Any file you have lying around will do. Rename it something like "speedtest.exe" (this file will never be run, just saved). The one we use is just over 11MB. You need a file of around that size to do a decent test. Link that file so that you can pull it back into your computer as a "save" download to your c drive. Each time you bring it in for another test just overwrite it. Check the speed it comes in at. Whatever that speed is, that is the speed PlusNet is supplying. If that speed is slow you should Ticket them.
As for the speeds for P2P etc. They are slow. P2P will never be near your normal speed. No matter who your ISP is.