I reckon you're p*ss*ng in the wind if you think you can predict this. Yesterday when I was running over the Cavalcade route for one last time, they were hiding in a little village in the middle of nowhere. During last year's run, we found them on a junction on a road which normally is flic free. Just save your speeding for places where you're sure you can see that there are no blue vehicles with their noses poking out of hedges!
In general though, they seem to favour downhill stretches, villages in the middle of faster roads, and - recently - motorway service areas. Another favourite trick is to lurk just beyond the location of a fixed speed camera when you think you're safe to speed up again.
Don't forget - when you pass the village signs it's 50kph, unless it says otherwise!