Hi I am also in Torbay and am preparing my Yr 5 DS for the 11+. I am currently doing 1/2 an hour per week per subject. So 1 1/2 hours in total. I have no idea if this is the right amount or too much or too little! So far he seems to be making progress so I'm going to keep doing that amount for now. My reasoning was that it was about equivalent to spending an hour with a tutor plus the homework they would set. I will probably increase it in the summer, so he can do some full length practice papers.
The Devon forum always seems really quiet, although I'm usually lurking!
But I'm a bit wary about offering advice as it's all new to me!