I wouldn't worry about it too much. Train Driver vacancies are rare, and often times when they recruit it could be either internally or for qualified positions only. Sometimes you'll get an external position with Northern if you're lucky though, especially when they share depots with big intercity operators who like to take qualified drivers because it's cheaper for them.
Personally I think one of the reasons the job is rare is because it tends to be a job for life given the union protection and lack of redundancies (let's face it, there'll always be a need for train drivers so long as automation doesn't come in). Not to mention the pay is substantial, so those who have no further ambition might just want to stick with the job for the money.
Although, given HS2 will be arriving within the next ten years I imagine they'll be taking on new drivers for those trains, or they'll do what Eurostar does and take those with experience of high speed trains. Either way, the drivers are going to come from somewhere, so if you live within a good enough proximity to the areas which will be affected you might just be able to catch a vacancy if you're after one. All the best regardless though.
