Hello again ww
Its pretty much as AC says. I have found that over the course of a year you will get £200-300 flight pay per month. I haven't been doing many nightstops over the last year to give you some idea, not rostered ones anyway!
For a couple of months last summer i was taking home an additional £200 or so a month from roster disruption payments to give you an indication of the general chaos.
There is no overtime, not for pilots anyway. They can extend your day at any time and if it's legal you are expected to do it.