I returned a few days ago from Malaga on a Jet2 -300. Probably about 25 years old, looked like new inside, a credit to them that them have kept them in really good shape. Spotlessly clean as well.
I returned yesterday from Stansted on an Easyjet flight operated by Titan, a 737-400. Again in really good condition and very clean. Goes to show some airlines can have a tidy cabin if there is the will there to achieve it.