It really depends on the format of the test your DD will be taking. I don't have any knowledge of the Kent test, but DD has just sat the 11 plus in the West Midlands, and it was a CEM test of verbal reasoning, non-verbal reasoning and numerical reasoning. It is computer marked, and the vast majority of the sections are multiple choice, with only one maths paper where you have to fill in numbers in the boxes.
For this style of paper, there's little point in doing 'free text' workbooks other than for general practice. Having said that, DD used workbooks from a variety of publishers, to give a range of experiences and approaches. We all liked the format of the CGP ones more than Bond, but we used both, plus Letts, Collins, Schofield & Sims, and First Past the Post. We found 10-minute tests very useful towards the end.
For the CEM test, timing was the main challenge, so we were strict with that towards the end. DD also sat a couple of mock tests at local centres, to give her a feel for the exam conditions.
So, my main tip is to find out more about the test your DD will be taking, and choose workbooks that more closely match the types of questions.