It's interesting to compare Monarch with Jet2. Monarch came from charter, and have gradually morphed in to a completely scheduled carrier. Arranging full holidays are an afterthought, but nevertheless important. Cosmos uses other airlines when necessary to sell its holidays (but I'm not sure whether Cosmos joined Greybull when Monarch did).
Jet2 on the other hand, started as a loco and has moved in to holidays in a pretty big way. Their expansion into BHX and STN this year is heavily holiday-orientated and they are directly targeting Thomson and Thomas Cook.
Of the two, I suspect Jet2 is performing better financially.