Bad timing - you've missed most of the activity by just a few days, I'm afraid.
While the WCML was closed at Carstairs, several pairs of 90s that would normally operate
between Crewe and Coatbridge were temporarily transferred to Crewe to Ipswich diagrams,
but with the WCML reopening this Monday, most of them are working north of Crewe again.
Your best bet for daytime class 90s south of Crewe now is 4M63/4M87/4L90,
but any or all of those trains can be class 66-hauled on the day.