We found the bond books (11-12) were helpful as were the IPS series of test papers. Obviously the past papers are also invaluable and there is also plenty of donwloadable material from this website.
We are about half way through the Bond 10-11 papers-would you say the fifth papers are more like the level expected from the Essex 11+?
Yes definitely and may even be worth considering progressing on to 11-12 as this helps deal with the stretch or alternative style questions that may be put in to the paper. Bond also do a good ten minute test book which we found helpful.