None of this is intended as a comment about Whizzard as I know nothing about them, it is intended as a general comment on the subject of paying up front.
Saving £80 at the risk of £2500 at the start of that two month period is in my opinion only worth doing if you have some personal guarantee from a director of the company you are paying. A lot of people got burnt from a company collapse that could be seen coming from miles away last year and they had all paid up front. A similar thing seems to have happened in the US earlier this year.
Some schools need to offer up front payment discounts to continue paying their bills, and if their customers start to tighten their belts due to the credit crunch, there will come a point were they can no longer meet their liabilities and the customers end up out of pocket.
I did a simlar thing to you, although with far less fixed wing experience, and managed to do only 5 hrs per year for 2 years. I then went to one hour a week and started to make progress quite quickly, I got through at 36hrs (coz you could back then). My experience as an instructor is that most experienced fixed wing pilots once they are aware of the difference make quick progress, but find it harder than they expected to.
Cheers
GS