Evening
You'll just need to check in the respective sites regularly on their careers board. Northern & TPE are your best bet. You might be in for a wait though - Northern have their change over at midnight tonight from Arriva to the Operator of Last Resort and the recruitment system is presently on hold for a short time. TPE advertised for 30+ vacancies for trainee drivers in December so it's likely they won't recruit again for a while. The other Yorkshire TOCs (LNER, Cross Country & Grand Central) don't seem to recruit trainee drivers at all. You need to be mindful that these trainee vacancies are very much sought after & don't stay advertised for very long.
CJ