If you can save £200 per month easily for the next two years, not only will you have two thirds of the money needed to get your PPL, you will also KNOW that you can afford the hobby. Start saving now and be ready to start learning in earnest in the Summer of 2012. Having the funds ready will allow you to fly as much as the weather allows.
That's how I did it, and it worked very well.
After the frustration of being able to afford only one hour per month and nothing to DO after getting all the theory stuff and R/T out of the way, I stopped and saved up for two years. Then I booked lessons almost every weekend, and finished inside of three months.