Historical Enquiry War of the Roses

Hello

I need help setting out a question and sources for my historical enquiry. I will be doing it towards the War of the Roses as its something that seems incredibly interesting and fascinating. It pretty much IS game of thrones.

What is a good question that spans 100 years?

I am looking to buy the following texts:

http://www.amazon.co.uk/gp/product/0099540177?psc=1&redirect=true&ref_=ox_sc_act_title_1&smid=A3P5ROKL5A1OLE

http://www.amazon.co.uk/gp/product/1445646358?psc=1&redirect=true&ref_=ox_sc_act_title_2&smid=A3P5ROKL5A1OLE

http://www.amazon.co.uk/gp/product/1471838226?psc=1&redirect=true&ref_=ox_sc_act_title_3&smid=A3P5ROKL5A1OLE

http://www.amazon.co.uk/gp/product/0143127888?psc=1&redirect=true&ref_=ox_sc_act_title_4&smid=A3P5ROKL5A1OLE


Any recommendations? I don't want to spend more than £50 on books but am willing to go over it.