Lucy & BW,
Thanks for your comments, it's nice to put something back after all I have learned from this site and one local helpful parent.
After I had posted I thought I should have put more in about preparation, but did not want to scare you just yet.
I can understand partly the Reading advice that no further preparation required ( If your son has completed KS2 to a high standard, unlikely in November, and has a natural talent for Reasoning papers without having seen one, very unlikely ).
We overdid the maths preparation. We did lots of English but not enough multiple short comprehension, this format did not feature in our planning I had not looked at the KS2 packs sat on the shelf.
There is much valuable advice on this site and many good papers to download, the CD's arrived at the right time during the summer heat and helped re-start study, it became fun again.
During the year of study we had peaks followed by collapses in performance. I think it is best not to push for that extra 5% but make sure you are consistently above 80%.
The marking is I feel biased towards VR/English, if its one mark per question then its 50+65+85=200. Not sure all the essays are marked, this years was 'write about an electrical appliance that might appear in a museum in the year 2300' or words to that effect.
On exam day scrap paper is provided and boys are told repeatedly not to write on question paper. However if you email admissions they advise,
quote "Thank you for your email. We do ask candidates not to write on the exam papers and they are provided with rough paper for working out answers, however they will not be penalised if they do write on the question paper".
Only thirty one days to go to results day.