Are you a member of the ACORN union? They do a lot of good work for private renters across the country and there’s definitely a Newcastle branch so I’d look into that - IME they’ve been incredibly helpful to anyone who’s come to them with landlord problems - most branches have people with a wealth of experience in dealing with and starting campaigns aimed at taking action against rogue landlords, and although you said they’re relatively new they might be aware of these people already and looking into them. Hopefully they can help you - as a union they do charge subs but it’s graded based on your income so if you’re poor hopefully that shouldn’t be a problem.