Hi there - I would be really interested to hear what others say about this as this is just my humble opinion, having gone through the process last year and DD just finishing Y7 at Tiffin and DS1 doing exmas in Sept onwards.
I would say that the NFER tests are good preparation for Tiffin but the Tiffin NVR especially seems to be very tough. Excellent prep for the exam as has been said by others are the Daughtrey papers and Walsh especially for the challenging vocab. With regard to NVR it is harder to find more difficult material than NFER but others may be able to make further suggestinons for these - I wonder if anyone whose child did Tiffin this year could let us know the topics for the NVR. In the 2009 test it covered four sections, 20 questions each all in 50 mins with topics of odd one out, matrices, opposites and sequences (I think, but have hazy recollection now - my DD was upset as there were no codes)
What does everyone else think - Jays Darlin if you are out there you are always a mine of useful Tiffin info !!