Last time I heard any figures for Channex crews it was about 350hrs a year, but admittedlty that was before Jet2 was up and running.
Spoke to a Jet2 guy the other week based LBA and he said they were doing about 800hrs a year, but he was on a 'secondment' to a Channex mail flight at the time.
Suspect the current picture averages out somewhere in between, as crews appear to swap between the two operations on a regular basis. As an aside, haven't met an unhappy Channex guy yet - now there's a rare novelty in today's market.