In addition to this you also receive a payment depending on how many hours you fly in a month, currently about 17 pounds per hour for an FO.
So with an average of 62 hours a month this equates to another 1000 (ish) pounds per month, gross. deduct tax, NI etc and you get about 550 net.
A 6 year FO takes home ie. net between 3500 and 4000 pounds per month.
As mentioned above these figures can vary widely depending on pension contributions and your hours that month.
Hope that helps