Wheres the other 10?
Whereever your instructor thinks you need extra; dual circuits, navigation or solo.
So am i right when i calculate i would pay 25x£215 and the rest would be at £165 as i wouldnt have an instructor with me in the helicopter
However, your instructor is still on duty on the ground and you are flying solo on his licence so, in this circumstance, you would be charged dual rates.
Cheers
Whirls