I'm not sure if this was set in stone, but when Britannia were running their sponsorship selection earlier this year they stipulated that applicants should have no more than 30 hours flight time (something about learning bad habits!). Can't tell you if anyone was selected with more than this though, or what other airlines say.
If you can afford to keep flying after getting your PPL, get IMC etc I can't see that airlines would find any point in 'sponsoring' you as you will be well on your way to getting that licence, as opposed to an ab initio student. Not 100% sure about this though...
Good luck with the qualifying XC!