As I have seen people kiss godbye to large sums of money by paying "up front" I have to advise you to pay as you fly and do this by credit card as the credit card company offer some protection if the company you are trainning goes bust.
You say you are paying as you go which is a good start but just to get this clear for any one else who is about to start flying trainning!
Don't pay up front & use a credit card.