I noticed that you are located in Lancashire... may I ask what airfield you are going to be training at? The reason I ask is that I know of one particular FTO in Lancashire that you should
definately steer clear of.
I paid for my PPL in similar installments and luckily I didn't get burned... However, a lot of people who have paid 'upfront' have, hence the advice so far, it definately depends on who you choose to train with.
Good luck with the training!
Happy Flying
SS