Well how about Monarch operating the aircraft as ZB but with Thomas cook holidays have 80% seats onboard the aircraft?
Possible maybe
Do Monarch charge any extra for checking in at the terminal instead of online (like Ryanair do)? I ask as when I try to check in online I'm forced to pre-book a seat as well, at a cost of £8 per person per flight.
There is no charge for checking in at the desk in the terminal. Unfortunately, like you say, it is only possible to check in online if you purchase allocated seats onboard for a charge.