Stuart, with regards to the radio side, I really worry about having anything other than the book.. It includes everything you need to know and you will find you pick up most of subject by just flying in general. The exam is probably the easiest, so I wouldn't worry too much.
The Navigation equipment needed is pretty much what you already have; however you will soon be doing diverts and that requires a different piece of equipment: a DP-1 (it's basically a protractor and ruler moulded into one..
Hope this helped. I'm by no means a pro!