Regarding the training; For the 19-weeks or so classroom training you'll be based at one training academy (Bristol, Reading, Plymouth (I believe?) or Newton Abbott). There will be a couple of weeks throughout this time that you'll be at your Home Depot from front end riding and maybe a week's leave, though. You'll have a couple of days for corporate welcome etc if you're external to GWR, plus some tablet training which will likely be in Swindon.
If your training academy (or any training such as welcome and tablet training) is more than 90-minutes from home you'll be supplied accommodation (as I am) Sunday to Thursday. There may be more than one course starting on the same date for different academies so you may find that not everybody here for the 2nd of December are all going to be on the same course. There was a Reading course which started on the same day as my Bristol one back in July. If that's the case, you'll be on the same corporate welcome, but will then go your separate ways.