Unit training depends entirely on which unit you go to. You don't get a choice - you can select a preference, but you'll go where the company needs you to go, which may well mean uprooting your family.
With regards to Swanwick, it can be up to 6 months after leaving the college before you get on to a 3 month training course in the sims, then you're looking at least a year from the end of that. That's a best case scenario and assumes you don't fail any of the assessments on the way, if you do fail one then add a couple of months on to my numbers. Of course you've already done at least 9 months at the college, more if you've failed anything, and then there's a chance you may be kept waiting before you join a unit. It took me 3 years and 5 months from starting with the company to validating at Swanwick, although the college course is now 6 months shorter.
Regarding your salary progression, it jumps from the starting wage once you leave the college to around double that and then when you validate atr your unit it goes over £30k. If I remember correctly, if you validate within three years of starting with the company you'll stay on the 30k+ and then after your three year anniversary you jump onto the ATCO scale which is a significant rise, but varies depending on where you're posted by around £5k, it's still a nice pay rise whichever way you look at it