My thoughts are that Gilchrist was always worried about his finances. He patently wasn't "poor" but he was always worried that he mightn't be able to continue his studies. So, I think studying for his degree was his first choice but he was being sensible and looking at other options. Or perhaps though he was applying for the commission now, if he was successful he intended to ask if it could be postponed until he had received his degree. Which I imagine the Rhodesian police would agree to - they'd prefer to have an educated man.

I don't think personally that trying for the scholarship was his last attempt to stay - that if he didn't get that money he'd have to go. It's just that suddenly temptation was put in his way, and because of his constant anxiety the money seemed more important than keeping to his own set of morals. I don't think he was thinking clearly about his future at all really - commission or studying. He was just caught up in the moment and the hope of receiving the scholarship money. He couldn't think beyond that.