therefore I politely asked the lady at the Flybe desk if she could change my return flight to an earlier departure
Rawtenstall - understand the point you're making perfectly, i.e. "Don't bite the hand that feeds". Just one point, would the lady at the Flybe desk be a Flybe employee, or has the job been contracted out? If so, probably wouldn't have the authority to use her initiative and less likely to see the bigger picture of trading £40 for a bit of corporate goodwill.