Both schools do their own papers so you need to practice all of the different types of VR. When we were going through this last year (can't believe how quickly time flies
) I got my DS doing Bond and Susan Daughtry. I also downloaded various papers off the internet and he practiced thosed during the summer holidays.
On the plus side neither WCGS or Wilson's test on NVR so unless you plan to sit your DS for another school that does test NVR, it's one less subject to worry about!
For Maths, DS worked his way through the Scholfield & Sims books - he was just finishing up Book 5 by the time he sat the WCGS test. Again, we downloaded various papers off the internet which he sat throughout the summer. You can find these on this website plus try googling 11+ and entrance exam papers (DS did some of the entrance exams for Dulwich/Allyns etc as well).
For English DS again did the Bond (I found these really hard but luckily he had a tutor for this bit!) Reading Comprehension books and I also got him writing 20 min essays. I found a number of titles on this website as well as others for ideas and he would have to choose one and write a story. He never really wrote more than a side of A4 but it was good practice for the exam as they only get about 20 minutes.
I can't comment on CAT scores but DS was at Level 5 for Maths & Science at the end of year 5 and I think he was a 4B for English (weakest subject).
DS got a guaranteed place at WCGS but just failed the Wilson's exam (have to be honest and say that we did slow down after the first result though and lost interest a bit!)
You may want to sit your DS for the Sutton Grammar mock test that their PTA run (have a look at their website) as it is good experience for the DCs. Also, visit the schools and see if they appeal to you and your DS.
Hope this helps - good luck.