You don't need all the books! IPS. AFN and SD Bright sparks all have the 21 types for VR as well as the GL Assessment/NfER/Letts papers. There are fewer practice materials for NVR.
Here is a link to a rather old post where people are discussing the books they have found most useful - I think it is still a good starting point.viewtopic.php?t=5540
There is also quite a lot of useful information in one of the stickies above:viewtopic.php?f=21&t=4525
If you are still stuck, ask and we will try to help.
Are you expecting to be posted to Coningsby, Cranwell or Waddington? Coningsby is right in the selective area; Cranwell would normally have no problem getting into the Sleaford schools but Waddington is too far away from any Grammar Schools to be absolutely confident of entry and most people there go for Priory LSST instead.