Learning to fly is an expensive business and if I was looking to save money I'd try and spend more time at the airfield chatting to pilots or instructors or trying to piggy back on someone else's lesson to make the time spent in the air as close to the 45 hour minimum as possible.
I would be worried that the 2004 material (which was about the time I learnt to fly and was reading material) will be out of date. Sure, things like the principles of flight don't really change but the terms and the content of the examinations do. Is there really much saving to be had by buying old material as opposed to the risk of learning something that might have since changed? There's a lot to learn so best to only do it once in my opinion.