I assume it's going back beyond many of the interesting examples in this thread - but did what I think was the LNWR service to/from Nottingham London Road Low Level Station (now the Virgin Active Gym) provide for services to other destinations from Nottingham not mentioned above?
The L.N.W.R. (and the other railways for all I know) provided through coaches on what now seems to be am amazing scale; the Railways Archive is in the process of posting on line Accident Reports and the older ones provide, by chance, insights into the then-everyday workings that have long disappeared and these include through coach working when describing train formations. - and, as an aside, also showing how quickly Normal Working was Resumed then!
For instance, the accident at Melton on the Joint Line on 25/7/82 involving a Nottingham - Northampton train refers to it attaching two through coaches and a brake van at Stathern. The coaches concerned were Scarborough to Northampton and Scarborough to Leamington ones, and had presumably arrived at Scalby via the G.N. and Newark,
I've the Marshalling Circular and Train Working Diagram books for a particular summer in L.M.S. days, and these show that the trains commonly known as the "Sunny South Express" (there were two) still had a large number of through coaches attached and detached en route, and coaches to/from Scarborough were still attached/detached at Northampton. The Joint Line was clearly not just regarded as a local branch.
On the subject of the Joint Line, rather than Nottingham, it was interesting how the G.N. tried to keep revenue 'in house'. Trains from Leicester to the Norfolk resorts were routed G.N. to Marehay then Northwards over the Joint, then onto the G.N. circling around to pick up the G.N. & G.E. and then onto the M. & G.N. Presumably half the revenue was better than none even though the routing was circuitous (particular compared to the rival route via Peterborough) and co-ordinating loco and crew diagramming must have been stressful!
Getting back to Nottingham I think it very likely that there were through Euston coaches from Nottingham via Northampton. This might have been a shorter (in distance terms) than the Midland routes bur presumably the overwhelming Midland influence in the early L.M.S. (or Greater Midland Railway, as they regarded it) soon saw off the former rival route.