There will be a number of things that will determine your pay (East get a different deal to West). Shift times vary from depot to depot. Man Vic's earliest is around 4am for guards, but Liverpool Lime St has a 03:12 start.
Don't know if this is the case for all depots, but most of the ones I know on the west are divided into links. The newbies start in the bottom link and when vacancies become available in the top links, they move up based on seniority. Most of the time you find the bottom links get the dogs end of the shifts, but as most of them say, "We've all been there"
Good luck to those applying! I know these talent pools seem frustrating, but it'll be worth it in the end and I think there will be a big recruitment drive into next year.