I have used NHS hearing aids for the past nearly twenty years. Over that time, they have got smaller and smaller and more and efficient. I have seen some friends pay thousands of pounds for aids, which appear very little different from the ones I have. AND......as has been said, aftercare is excellent with free provision of batteries, etc.
I accept that my own hearing is getting worse and worse as I age, and that the aids can only work with what they have.
However, couple of things that any user can do to assist this.
Ensure that the little tube in the hearing aids are kept clear, they block up very easily which makes that aid to perform badly. Equally, check that your ears are not gunged up. Think we have to pay, these days, for having ears syringed, but worth the cost if it helps hearing.
All hearing aids are just that - aids, probably not going to give you back perfect hearing. Wonderful in my own home, or on a one-to-one, but I have always found difficulties with these in noisy places (ie: pubs, cafes, large meetings). Background muzak is a total nightmare for me. However, without these aids in my ears I would be much more isolated. Audiology seems to be one of the few NHS services which works in the way it is intended - free at the point of need/use.