First of all don't buy a student starter kit for several hundred quid! Nearly everything in it will prove useless to you at a later date. From my experience I suggest the following.
The Air Pilot's Manual book 1 contains the syllabus and a guide to lessons so that would be useful. See if you can find it on eBay second hand. I'd suggest that method for obtaining the other books as well, and I'd suggest going through them in order. If you can get the first two books done and get onto the navigation book by the time you're doing circuits then you'll be ready to go on navigation lessons after your first solo. When you get the navigation book also remember to get a CRP-1 whizz wheel.
A kneeboard would also be useful, but ask your instructor to show you what PLOG's the school uses so you can buy an appropriate size. You won't really need it until it comes to learning navigation but you probably will need to have something you can write down radio stuff on and they are pretty cheap.
I'd leave everything else until post solo. When you start navigation and only then, buy a map, plotter (something small enough to use in the air during training/test), and a marker pen/pencil.
If you haven't given up by this stage a good headset would be a worthwhile investment and that is about it.
Depending on where you live (close to the airfield?) an airband scanner may be a good idea for developing radio listening skills and also to check the local weather. Might be a good thing to get along with book 2 for when you learn about meteorology.
Hope that helps give you some idea.