Ok, no panic, you have lots of time, as they will not be doing their test until Sep/Oct 2012. The advantage you have is that in Bucks you only have to do Verbal reasoning.
You also get two chances, so you can have a bad test and still pass, if the other one is good.
VR is one of those things that can be tutored, and if you have the time, you could easily do it yourself. There is a wealth of resources (You can get a lot of help from this website, for example) and "How to do" books.
I have tutored both of my boys at home, and while it was a bit daunting to start with, once you start doing it is actually quite interesting.
Each person does it in a different way, but we worked on all the different question types first, and once they were familiar with these, we started doing test. If you start doing test without really knowing the techniques behind each type, unless you are a genius, you will find it hard. (I did
Once you know what you are doing, is a case of getting the child ready for exam itself, as you have a very short time to answer each question, and time management is almost as important as knowledge.
I am sure lots of people in this site will help you if you get stuck
Having recently moved away from Buckinghamshire, I would add the Cottesloe school in Wing (not Grammar) is regarded generally as a good school.