A long time ago when I took my DC to uni, the house we'd rented for him was almost identical (no rats) on arrival to what you describe. It stunk of overflowing sewage, the carpets were sticky and crunched underfoot, and the cupboards were infested with beetles.
I hit the roof, and asked the LL who was there smiling a welcome and pretending not to understand what the problem was, if they would be happy for their own child to live in such filth and pay for the pleasure of doing so.
I then called the agency and demanded that they find a clean, well maintained property right there and then - it was out of hours at this point, as we'd driven a long way - and surprise, surprise, they managed to find just a one....threatening hell and damnation probably helped, as after driving nearly 400 miles on several major, road blocked motorways I wasn't in a mood to compromise.
They probably thought that as we were out- of -towners and were arriving last minute, that we'd accept it without a fight.
Once my DC was settled, I contacted the local Environmental health, with a description and photos I'd taken of the festering dump, and got it taken off the student accommodation list.