Old thread, but HuntyCat, I think you are totally wrong about being at a disadvantage.
I have a huge library of books, many gleaned from jumble sales. Books just aren't valued at all. Go along to a jumble sale at the end, and for £1 you can fill your sack with the leftovers - always huge numbers of lovely books. Your children's school will have heaps of books you can borrow. Organise an after-school second-hand book sale.
Re tutoring, we DIYed due to cost, and my DS got into a superselective, ahead of many prep school children and those who had been tutored from Y3. (We even picked up practice books from the jumble sale!) In fact, I think that those who DIY often do a better job than tutors. Go to the eleven plus forum, and get tips and advice. You don't need many resources at all, and there are lots of free ones on the internet.
My DS is in Y8 now, and loving it. He has lots of friends, because he is no longer one of the "nerdy ones" - he's just average, and fits in really well, which is great.