BALPA will help you with the payscales, otherwise a "search" will uncover the answers for you. Take home pay relative to years of service, base etc etc so difficult to quantify. Range from £2000 up to £3500 net in ball park figures.
Generally happy bunch, similar problems to most like charter airlines. Probably happier than most as owned by huge Company, solid history (40+yrs) and most importantly profitable. They are recruiting, not laying off so happier than most.
Time to command, dead-mans-boots. Current PC's being promoted probably average 14 yrs with Britannia. Quite high retirement bulge, but anyones guess mainly due to uncertain expansion plans. Expect 10+yrs if you joined now and you will not be too far wrong.
Basing policy, "review in progress forever". Big bases remain LGW and MAN. Crystal ball stuff really.
Hope this helps.