Morning
Northern do normally reply back in a few weeks. I've dipped three applications this year - sadly I didn't get through the paper sift stage which was extremely disappointing.
I submitted the last application on the 3rd May and they sent me the rejection e-mail last Friday, which was the 7th June. This was five weeks exactly. They do give a time scale of 2-4 weeks to get back in touch but because of the volume of applications for various jobs they may take slightly longer to contact you.
All I will say is good luck but please don't get your hopes up too much as many people, including myself, often find the application process is extremely hard to get through.
Best of luck.
C J