Just to add my two pence to this:
The choice at a well known BA franchise is
1. Say no
2. £460 gross if you want your hours to count towards the industrially aggreed 775 hours plus flight pay.
3. £139.50 per flying hour gross if you don't want it to count towards the hours i.e. a longish flight will drag in £1300+.
AND YOU GET AN ADDITIONAL DAY OFF OWED IN OPTION 2.
