Riddster, I am a wannabe like yourself so don't take my info for gospel. I got it from
http://www.pilotjobsnetwork.com/.
According to the website starting FO salaries are between £30k and £35k a year for Aberdeen operators. Bear in mind the info might be out of date or the fact cadets might start on reduced salaries. I don't really know!
On OAT's messageboard there is a post saying more info will be made available to those who attend stage 2 of the selection process.
Good luck if you decide to go for it.