Oveur
I was in an identical situation to you, girlfriend of 3 years. I had a lame job and wanted something more.
I was on the CTC scheme and went to NZ for the best part of a year. Granted she cheated on me while I was away, which wasnt great and we then broke up but I'm now with the most amazing girl, flying planes and overwhelmingly happy. I shudder to think what would have happened if I hadn't gone.
If you don't do this flying course I'm going to come round to your house, pack your things, put you in a bag and force you to do it. I'm not joking. You will only regret it. Imagine if this girl leaves you 6 months down the line after you've sacrificed your dream? Not worth considering.