I have personal experience of a "struggle" with a certain school after paying up front.
Sometimes, discounts are available for advance payment and then it is best to pay with a credit card. If the school doesn't accept credit cards then that maybe enough to make you consider elsewhere. There are places that don't wan't the full money upfront for a PPL, Britannia is one of several.
What if you pay in full upfront and you find that flying is not for you? What do you think your realistic chances are of getting a refund?