Salary varies from place to place, but at non NATS units expect between £10K to £14K inclusive of shift pay - sometimes more, sometimes less, additionally, it's very rare that anyone will give you any relocation expenses.
Top tip: Don't ask the question at the interview, let them tell you.
Remember that, in common with many other professions where an opportunity for career advancement and serious money is available, you can expect the base salary as you are starting at the bottom the queue.
How you advance is entirely down to you.