F/O on a jet with a regional airline should pay £28-35k...
If you can get into a charter outfit flying 757s you could be looking at £45k+, but this often depends on the experience you have on joining and whether you're bonded for a type rating or taking a reduced salary to pay for it!
Remember that a lot of airlines pay duty and/or sector pay on top of your salary and this can add a couple of thousand or more depending on the deal...
Good luck!
LKM