I completely agree about the travel environment in a Scotrail v a Northern 156. If I have an option I use the Glasgow/Newcastle train for my journey to Carlisle/Newcastle. Original (low back) seats, but always immaculately clean and this far more pleasant. Northern trains are, except a few 156s that seem to have had deep cleans and the truly dreadful bus seated ex-FGW 142s, the dirtiest trains I have the displeasure of using. I did travel London Liverpool St to Southend in a filthy 315 (one) and had thought how unlucky the Anglian passengers were to be getting Abellio - until that journey. I quickly realised that they would note no difference. Northern and one had similarly filthy trains, inside and out, so the same company in both areas would not mean a drop in standards!
I wish someone would start pointing out how awful Northern is, as a company that is, great staff. Old trains (please, oh please scrap the Pacers, I pay the same, or more, than the SE commuters, but they get refurbished 313s, 455s, recent and excellent 377s and 440/450s we suffer still) and filthy trains. The stock in Yorkshire and the North West seems cleaner, but still the Pacer is around there too. Why can't Heaton clean a train?? If you are reading this try speaking to Scotrail, they seem to know what water, detergent and some care can do.