The long-term answer would be to change ISP. But if you're contracted for a particular period, then I'd spit dirt at them & demand that they stop filtering your service. I don't know what consumer laws are like in UK, but I wouldn't be surprised if it's breach of contract. If they offer unlimited downloads & offer a specific range of speeds (& pretending they don't block p2p on their FAQ page) then I believe they are definitely breaching consumer law & contract with you. In those circumstances you could legally break from their contract because they haven't fulfilled or aren't fulfilling their contract. They have made an offer of guaranteed services, you accept, but they aren't fully delivering on the promised service. But they may have some fine print somewhere in the agreement to hide behind

In any case, I would be loud to them & demand they stop filtering or blocking your p2 connections.