Nice! I really like it!
I'd suggest you don't use a premier high-speed passenger locomotive for freight duties.:hehe:
By the looks of you're carriages, you're in the BR blue era as well, so you should probably be using blue locos.
For freight duties around that era a class 37 in BR blue should do. These work pretty much anywhere.
Maybe a BR blue 'Hymek' for the passenger (search the DLS) though it depends where in the UK this is.
The 'Deltic' (class 55, the one you're using) is a high-speed passenger loco, for mainline duties, not branch or freight.
And maybe put some greener textures in, it can get pretty wet hereabouts.