If I can just voice my views on the X12. I've not used the service between Durham and Middlesbrough before (as far as I can remember anyway!), and one of my aims for the next couple of weeks is to ride the Durham to Newcastle section, now under the X12 as well. Despite being no Arriva expert, I have actually used the service between Chester-le-Street and Durham (and vice-versa) quite a lot, enough to be able to say that heading back from Newcastle, the service seems to have relatively good timing. The 26 and 56 minutes past departures from Chester-le-Street that I've used on Saturday mornings have always been prompt, although often having just a minute or two to spare.
However, I can't say the same for heading the other way. Sometimes when I've been sitting around in Durham Bus Station for a Newcastle-bound X2, I've been waiting as many as 10-15 minutes. While this has not always been the case, the service has never really been bang-on with the timings advertised. In my opinion, the service seems to almost pick up some time when heading to Newcastle, and back, so when I've seen the service heading to Durham; it's been relatively on-time. It seems to me that there is something on the Middlesbrough section that is corrupting the schedules, and this maybe needs to be looked at.
I have to say I also agree with Jimmi's point about omitting Birtley. Whenever I've passed through on the Arriva services, in both directions at a variety of times during the daytime, there have never really been great numbers of passengers boarding or alighting. If the service was to directly follow the ''Pronto'' X21 route from Chester-le-Street, using the motorway to get as far as Low Fell (as there does seem to be something of a demand from there onwards), it could possibly help timings even further, and if it were to be a direction competitor with Go North East's X21, using, let's face it; better buses - I would most certainly start using regularly. Although, if you use the A1, there's never a guarantee you'll not face huge amounts of traffic, would be a bit of a gamble but I think in the end that could be worthwhile.
RE: Arriva North East: Rare & Odd Workings - April 2015