Patient Confidentiality - what happens when they are 16?

My son has high functioning autism.  He is currently 15 years old, he was diagnosed after a long fight at 12 years old.

Today I booked a GP appointment to discuss his skin picking activity.  I wanted to discuss the skin picking with the doctor without him being there as I was worried it was self-harming and I don't like talking about him in front of him.  When I checked it was ok for me to make the appointment in his name, the receptionist pointed out that if he was 16 they would be bound by patient confidentiality and I would not be able to attend on his behalf.

In less than 10 months time he will be 16.  He will not be able to independently attend a doctors, hospital, dentist appointment and successfullly discuss any condition he may have.  He will however be bound by the rules of patient confidentiality.  I am looking for help and suggestions to avoid a potential problem in the future.

Thank you

Debbie