Hello. There are lots of hearing aid threads already on GN. If you Google, Gransnet, Hearing Aids you should find lots of useful information.
I've had two aids since 2007. The first ones were private. For the past four years I've used the NHS aids. They are small, no one realises I wear them, easy to use and better in every respect than the first ones, which cost £3000!
The batteries can be obtained, free of charge from the GP surgery, but I find it more convenient to order my own online from Specsavers. They are not expensive. Hope this is useful to you. Hearing aids are life changing.