mad bear,
In terms of your meagre budget. I can see your thought process and your reasoning, but I didn't even consider navigation until I'd finished my solo circuit consolodation. I did what I needed to when I needed to. I also finished my PPL in 45 hours. Again knowing me and my limitations I would've taken longer if I'd have tried to do it all in one go.
obviously my advice and pistonones "Fly the numbers" are very much contradictory.. use what's best for you!