there’s one in Salford mate next to the train station (Salford Crescent) and there’s one in Preston (at the station)
Grade 2 salary is around £32k. This is paid every 4 weeks (next pay day is Friday 13th Oct, then every 4 weeks after that. This is the very basic that you’ll earn. Once you’ve passed out of your box then there’s loads of enhancements, but while training it’s a flat rate of around £32k
With regards to your interview, have a read up on this thread. There’s loads of info. I would say the key things are safety (safety vision, life saving rules) what train operators are running, why you want to be a signaller, what draws you to the position ect. Are you happy working shifts (this is massive, working 12 hour days, sometimes 70 hours per week, depending on if you like to smash the overtime, this can be a mix of day and nights)
The interview is around 40 mins or so, but try to ask them a few questions after, nothing OTT, just a few basic ones to get across that you’re keen.
Good luck