Don't go to BT thinking that by doing it you're cutting out the middle man.
Openreach is the useless arm of BT and it has a monopoly on a lot of the infrastructure. It is NOT the same business unit that deals with domestic phone/broadband contracts. Whether you go with Plusnet, BT Retail or anybody else, chances are it'll be Openreach who screw things up, kick deadlines down the road, etc.
The railways are an equivalent of sorts - Network Rail is the agency responsible for the infrastructure, the train operating companies run stuff on the infrastructure. If the signals go down on the east coast mainline ALL trains from ALL companies that use that signalling are affected, and it wouldn't matter which train you were on, you'd have the same problem.
This is why there is such a strong lobby for Openreach to be broken away from BT completely because as things stand, people are being misled simply by BT Retail and BT Openreach both being BT companies - they think BT Retail has direct access to BT Openreach in a way that Plusnet doesn't, but this isn't true.
