As I recall, the bus route from Glossop out to Holmfirth only runs at certain times?
A lot will depend on what you prefer to do, and how far you want to stray from the rail network. As Ianno87 says, there are a number of excellent bus runs through the Derbyshire dales, and the 58 between Macclesfield & Buxton is definitely worth a go. Getting to Ashbourne is do-able, but probably best via Buxton as there aren't that many buses via Leek these days.
As for the ticket, it's a very good value ticket that covers a wide area - lots to do. Just be careful if going out to the extremities, such as Burnley, as you're limited to certain operators that far out. Don't be too surprised to have some bus drivers do a double take or question it's validity either.