Oops, I've been tempted back to reply to LeQueen.
"If your child is genuinely academic, all they should need are a few past papers with which to familiarise themselves with the actual mechanics of the 11+ paper."
In my experience, this isn't true at all. It might be in your area, but it's not true in mine, sadly, where there are only superselectives. I was shocked to discover that even the brightest children have been tutored these days, even though few admit it. Perhaps it's the effect of the credit crunch.
Also, it depends on your DC's school. Mine hadn't actually covered all of the maths needed to for the exam, they don't do anything like verbal reasoning at school, and grammar doesn't seem to be taught at all. Luckily I realised the gaps a few months before the exam, as I'd been a pretty hands off parent who hadn't even bothered checking they knew their times tables.
Thirdly, in some areas, if you have an exceptionally bright child, a few past papers will be enough. But what about for a child who is borderline? They may do well at grammar school. However, they will not get in without a helping hand.
I don't advocate two years of intensive tutoring. But I do think it is misleading to suggest that all they need is a few past papers. It depends so much on their current school, the area and which exams are used to select the children.
PS Congratulations Learner Driver No More! No idea what all that cloak and dagger stuff is or means though