Jesus man 
Mind I can see why you might laugh when comparing to other North East wages, as it is a massive increase on the average regional wage. To be fair though when you look on a National average of what a Traindriver is paid, then the actual rise they are requesting has some substance. People could argue that is what they signed up for when they joined up, but the terms and conditions have changed a fair bit and will change again with the introduction of the new fleet. Currently your average Metro Traindriver is looking to move on within a couple of year to another TOC for much higher wages.
You would be surprised how much turnover there has been over the last five year especially. There is a big cost with training a new driver over roughly a 12 week period, having to do this at very frequent levels due to high staff turnover is not cost effective. There is also a requirement to have a stable and consolidated staffing establishment in place to ensure that there is full cover for the operation of the service, specifically with the introduction of the new fleet in the not too distant future.