Go to a large WH Smith's buy these tests:
10-11 years old, multiple choice, Non verbal reasoning packs and Verbal Reasoning packs both with 4 in a wallet. Do not get ones with Maths and English in as these are for other grammar and Inde schools exams.
There is also a very helpful 'How to do these style tests' book made by Letts I think so get one of those to assist you. Test packs are around £10- for 4 questons. As a guide I'd do a test every day now until the exam. There are also books in yellow and green that have 60 quesion tests and you circle your answer, these too are good practise but are not the same multiple choice format as the exam. Go over any weaker areas or incomplete answers, and try to get each quesion down to 30 seconds per question or less as soon as you can.
Tiffin Girls test is
50 mins of 80 questions in VR and 50 mins of 80 qestions in NVR with a 15 min break in between. Register with the school if you've not done so to do the test (can download the sheet from Tiffin's website for 2011) and register the school as 1st choice with your local ed authority if not done so ASAP. Hope this helps. Good luck BTW have met girls who got in on as little as a few test just before the exam it is possible.
Thank you very much for the suggestion. I got those books, firstly aiming at building the concepts and then in dec shall focus on tests.