3456 Vol A Fixed Wing Principles of Flight
Engineering Maths by Ken Stroud - to get your head around that kind of stuff again.
Intro to JSP 556 which explains the system of UK mil test flying regulation.
JSP 553 is worth a scan to give you an idea of the UK airworthiness requirements.
Flying controls section of your own aircrew manual.
If you are a J guy from Lyneham (as opposed to a TriStar mate who just happens to live nearby) then have a good understanding of the development history of your own aircraft.
Flight International so you have a clue what is going on in the Aerospace world.
Have a realistic idea of what you will be going to do when you graduate from Edwards.
Really really understand why you want to do this - because some of it is going to be mindnumbingly painful................but worth it.
Most important tip is to visit 206 and ETPS and understand what you are getting into and to steal all the tips that you can from recent graduates and the tutors.
Interviews are not looking for trained test pilots or FTEs but people who are suitable for training. No BS and be prepared to think logically on your feet.
The above is a long list which you are not going to complete in any kind of depth. Do what you can in the time available - some of the questions will certainly probe areas that you don't have the first clue about, just to see how you think.