Think I will lay my cards on the table, so to speak, in case it's any help to parents considering DIY tutoring for their DC.
My DD got decent passes for Denmark Road - 226, Ribston - 229 and SHS 241 ranked 122. She got 227 for Pates and didn't qualify.
In top groups of small year group - was level 4b at end of year 4 for everything but we never had CAT scores or any subsequent Key stage levels.
DIYing probably took about a year - but started in earnest in Jan. before the test. By this time we had already looked at each of the 21 question types using materials on a free site I'm not allowed to mention, and the Tutors beginner VR CD.
We did the 10 IPS 30 mins papers, which she scored approx. 90% on but could never finish in the time allowed.
We did a few tutors level 2 and 3 papers at some point.
We did I think 6 of the Tutors full length papers, and by the last one she was just about finishing in the time.
Then moved on to Bright Sparks, both packs, but mixed up with Walsh (papers 1-10, we used papers 11 and 12 as extra practice for certain question types) and towards the end, the 4 Nfer papers.
Somewhere I do have her scores for each paper, but she pretty much got 88-91% on the Bright Sparks, 91-95% on the Nfer and 84/85% on the Walsh papers. Timing was always an issue and she finished the second paper by the skin of her teeth in the test.
We used the Tutors level 4 papers to give her experience of dealing with much harder papers, and also to try and improve her speed.
We did try to improve her vocab by using the AE tuition Vocab books and we did some mental maths.
What would I do differently? Think I would actually do less...(or start later)..she was ready by mid August - nothing we did after that really improved her scores, and her timing only marginally - and we were trying to balance the possibility of 'burn out' with the danger of her forgetting everything.
Hope this helps someone, it was the detailed posts like this that helped me last year, so thank you to those who took the time to share their experiences.