Don't give up on the HPC.
They've got a stautory duty to investigate any complaint against a registered person which is in regard to their 'fitness to practice'. Doing a disappearing act with your hearing aid might seem to bring Ms Coper's fitness to practice into question. email
[email protected] or phone 0800 328 4218 to report your complaint.
However it's possible that the HPC might consider that your report relates only to 'consumer service'. which they don't regulate. Even so, all is not yet lost because Susan Cooper is also a member of the British Society of Hearing Aid Audiologists, who have their own complaints procedure:
http://www.bshaa.com/...aints/70/default.aspx
Chris