I worked for BT all my working life, so as an employee, I got free broadband, and never had any issues.
I do believe they are the market leader for a good reason, their service is the best.
Contact BT and get a price, then contact PlusNet and get a price, which will be cheaper, then go back to BT and ask them to beat it.
Chances are they will - as advised, it's a competitive market.