Some time before I got mine from the local hospital audiology department our lass had gone to Specsavers in response to deteriorating hearing. They performed various tests and suggested she needed to spend around three thousand quid.
She came home, made a gp surgery appointment and had her ears tested to a basic level at the surgery. They referred her to hospital audiology for soundproof room testing and she was prescribed a discreet digital aid. The responses were programmed to follow closely the frequency ranges determined by the test. Batteries last about a week and are issued free at the local surgery.
Some time later she complained I only heard part of what she had said so I followed the nhs route. After a few weeks bedding in time I wasn't happy with the high frequencies response as they seemed too loud. A return visit and the unit programming changed. All is good now and sounds I hadn't realised I was missing are heard clearly. All this was free via the nhs instead of a small fortune at Specsavers.