Some interesting perceptions above, but not all accurate.
I managed the move to Inter city driving, with less than five years railway service. Plenty of others have too.
Expect the companies to have several hundred CV's on file at any time. Competition, yes, but not insurmountable,
Clean, or near as, driving record. Flexible attitude. It's no good moaning about going five minutes over your day, with long distance work. When things go wrong, they do so in a big way, and the companies want people who will see the job through.
The trolley dolley to driver thing, is a bit of a PR myth. There are people that have done it, and that's great, but the vast majority that I work with, were recruited as qualified drivers from elsewhere.
Having worked on units, I find the Inter City work far more pleasant and varied, I sign more routes, and types of traction, and get involved in more interesting and challenging aspects of the driving task. My level of skill and knowledge, has significantly increased. As for money, far better off. The basic salary for a four day week (or near as), incl. Sundays, is just that. You get more money, for less hours, than the 4 + Sunday contract. The work is less demanding physically too. No sweat box 1980's units.