I work with a lot of people from Bishop Auckland, and most tend to use the Arriva 6, based on both price and frequency. GNE offer a Pronto saver for £22.50 a week, which is cheaper than a two zone Buzzfare (£24.50), but Arriva's weekly ticket is £16.90 (Bishop Auckland zones). 4-weekly would be £85.55 compared to £60.50. 

Looking at the Buzzfare zone map actually, it's perhaps an issue created by the zones not really being reviewed since they were brought in? Perhaps Tudhoe, Spenny, and Bishop Auckland should be part of the Green zone instead? If that was the case, then at £18.00, you'd be competing.