Honestly speaking, Gothicangel, what is your first instinct when it comes to what you're talking about here? I see you want to give readers a feel for Newcastle, and that's fine. But I also see that your writing is more about characters and storyline.
So how would you yourself, the creator of your story and your characters, instinctively go about giving your work the setting you want it to have? Would you deal with physical descriptions of places, buildings, etc., or would you be more inclined to discuss the people that surround your characters? In other words, what you would do yourself can be just as good, if not better, than what others might want you to believe you have to do.
Judging just from what you've said in your OP, I'd think you would be more interested in the people than the scenery. So, if this is the case, why not focus on the people of Newcastle? There is no law that says you must give detailed descriptions of the city buildings and places. You know what you're capable of better than any of us do; maybe you should ask yourself, "How would I do this?"
Good luck to you, and I hope you enjoy what you set out to accomplish.