I have just added this to the map of places to fly your drone at Drone Scene:
Land owner permission requirements unknown.
Knoll Beach is a well organised beach and, like all the beaches in Studland, it is owned by the National Trust. There is a large car park which is free for National Trust members but non-members have to pay £3 for 2 hours, or £5 for all day.
The post code is BH19 3AH