Marple / Rose Hill Marple really isn't that many diagrams - at best running half hourly - that is kind of why they are seen as routes ripe for Metrolink where the frequency could be increased.
There aren't many non electrified railways with much mroe than that.
The only major scheme like that left is TPE North electrification and that's completely dead.
~55 track kilometres gets you to New Mills Central and Rose Hill Marple via Hyde North and via Bredbury.
That gets you four trains per hour (I think, hard to tell for sure).
Rose Hill Marple has a cycle time of approaching 80 minutes, and New Mills Central I think comes out similar. So you will be looking at maybe 5 trainsets.
1 trainset, which might have more than one unit in it, replaced for 11 track-km is hard to beat elsewhere.
And track rationalisation could substantially reduce that if that was permitted.
Buxton no doubt comes with some complexity due to its length and terrain. Hardly an intensive service.
Well it could have it's costs reduced by track rationalisation.... but I know that is a dirty word these days.
Also the lines in the Hope Valley are bloody spaghetti......
If only there was some money to sort that out.