I used to work in the rail industry so I know how one particular company recruited and trained its drivers but it should be remembered that, as long as the national safety requirements are met, each company may have its own individual recruitment and training programmes.
Your boyfriend should first find out which train operators have depots in your area. (Don't forget that freight companies, such as English, Welsh & Scottish or Freightliner often require drivers). Most companies maintain a waiting list of people who wish to become drivers. Some firms require applicants to take aptitude tests before their name goes on the waiting list. Others only invite applicants to take the tests after they've been on the list for several months first. (One of the key parts of the aptitude tests is checking that applicants aren't too intelligent for the job! That might sound daft but very intelligent people often allow their thoughts to go off on a tangent. The rail industry requires drivers to have exceptional concentration skills which are often incompatible with very high intelligence).
As you've stated, driver training can take up to a year. (Yes, it's full time). There's a great deal of theory to be learnt, much of which involves memorising thousands of rules and regulations. Trainee drivers are paid throughout their training period although the rate of pay can be fairly low. (This will vary between companies but might be around �15,000p.a.). Once qualified, drivers quickly move on to much higher pay rates, with basic pay starting at around �30,000. With overtime and other payments, most drivers earn at least �35,000p.a., with some companies paying over �40,000p.a. to the drivers of mainline express passenger services or overnight freight services.
Chris