The Medway tests consist of Maths, English and Verbal Reasoning. The marks for the maths and English are doubled up so each count for 40% of the total, and the VR is worth 20% of the total.
The maths and VR are multiple choice, the English is written. You are correct that comprehension is not relevant. In recent years, the English test has required the children to write a letter or newspaper article (I remember my children said there were 9 different types of thing they might have to write - play, diary, letter (formal), newspaper article, recount - and I can't remember the others. Last year they moved the exam back into schools, so that most of the children took the tests over two days in school. But a good number took the test on Saturday and, probably because of this (because otherwise the children taking the Saturday test might have learnt what the English topic was) the English test was a story.
In any event, your child needs good vocabulary, grammar and spelling.
As to the Bond books, it is hard to answer that because the real questions are not available, and the children can never remember enough afterwards to be helpful (not that I asked!). But both mine prepared with the Bond 10 minute books and a few full length Bond or GL papers in the summer holidays and passed.
It is worth practising the multiple choice format to get used to it (tips like circling questions you don't know so you can come back without risking getting the answers out of synch with the questions, and what to do if you are running out of time), but the club may use standardized so they can see the working and find any errors.