There's no fixed 'base' depots for Northern 156s or 142s. 142s often travel around and spend time at different depots (since IIRC every Northern depot signs them they can go anywhere).
York and Leeds/Neville Hill crews do not sign 156s (the majority don't anyway) so they don't go there.
New Measurement Train, as mentioned above, is 'based' (don't like using that term) at Derby - ie that's where most maintenance is carried out and where the majority of turns start out from and finish at.
It's also worth noting that various units or locos will not end up at a certain depot all the time, mostly unlike buses. GC stable at Ferme Park as well as Heaton.
RE: Northern Rail
![[Image: 0a85ed5b4e97324e338555472f222830.png]](https://public.railmiles.me/signatures/0a85ed5b4e97324e338555472f222830.png)