Hello! I'm also from the Newcastle area and so far I've only sucessfully visited 2 places there.
As far as I know, there is currently only one left standing that I've visited and thats the abandoned Nightclub found on Milk Market near the Millennium bridge :)
There was an old Leadworks factory that I've been to a few times however last week I saw that it was now demolished after 40 years

I know theres an abandoned heliport but I have no idea where
I don't know if you've heard of the places in Durham, such as the old Elvet baths which I attempted to get into but I was caught by security and was chased lol. On the outside of Durham is an old College called Ushaw College (it looks amazing and I'm 100% wanting to go however no one is up for it hahaha) I've heard that theres security parked near the Public footpath in a caravan which is so weird but whatever. I'm trying to find people to go with because travel is expensive if you can't get the train.
More into the Gateshead area is an abandoned paintball site, if you check google maps, and simple look for 'Gateshead Mine' it's literally that site that you can see and the entrance is further around to the left side when you're standing at the bridge before it, I've been so many times and it's a lovely place to just get a few pictures and see whats left. It's also just around the corner from Pelaw metro. When you get there, there's a canny few signs saying 'Police Response Priority' n all that but I swear on all my visits they've never came, which was weird because when you're walking from the metro, usually 4pm time theres always a police car driving round, but no where near the site And if thats shaken you a bit, when you get to the site, if you look at all the lampposts, all the cameras have been ripped off so they literally don't know you're there hahaha. In Gateshead theres also a block of abandoned flats, however its like smack bang in the middle and I don't fancy having to creep around there at night, but you're welcome to do some research on the place! :)
Please also know that when you're exploring that paintball site, there tends to just be general public cars coming round because it's a well known shortcut, me and my friend were in once and there was a van and we thought it was security but it wasn't, the men driving came over and just simple asked if they were following the right route since their satnav or whatever was broke, so it's usually just like cars driving past it :)
In Sunderland, there's literally no places, apart from one however I don't know if it is abandoned or if you can gain access unless you do parkour or climbing. It defo looks abandoned but I don't know, it's just before you go round the corner to South Durham Flats, it's mad.
If you need anymore info, don't be afraid to message me hahaha, I could do with knowing a few more places but that's all I have. :)
Amber xo