This whole set-up is definitely NOT like the UK. I've done a PPL(A) and PPL(H), so I do know a little about it...in the UK at least. You take the exams when you want to and when you're ready. If you don't take them, you don't - no way can it be counted as a fail!!! As for this ridiculous situation of one instructor who's never there - forget it! Go somewhere else, even if it means a trip to another country for a few weeks intensive flying. You can't learn to fly this way.