The start is a good option as you can often mix with the riders and get the atmosphere. Most are friendly and will be OK with photos. If you want to get to a climb, I think you would need to be pretty early. The day before, at least, for the classic climbs of the Tour de France. The Tour of Britain will also be very crowded on the climbs. This is now a very popular race, and the entry this year is exceptionally good. The climbs slow the riders down, so you get to see more, but you would still be astonished at the speed they go up. I remember going to a climb on the Chase that takes me an age to get up, and the peloton rode up it chatting as if it wasn't there! Malvern? Give yourself an hour at least to be in a good spot. That is if you are going by bike. Several hours if you are taking a car.