We too are looking at sitting the test. At the open day the chief master said they would be 3 elements:
Maths - this will consist of 3 section, part 1 easy, part 2 middleish, part 3 is really hard and what determines the scholarships.
English - comprehension and essay writing, they look for complete sentences and for the essay part they give a topic and you have to write about it. They are just looking for good grammar, punctuality and vocab. Oh and the writing must have structure.
VR - nfer type stuff ( he also said we don't give too much attention to this section).
He then when on to explain how 1 child did very badly at his English and vr but in the maths section was very good. In his interview he showed determination and passion and that's why they took him on
he is now reading maths at Oxbridge!!
They gave some practice questions on their website.
Hope this helps, good luck