I recently had our bus driver on a RS tour (Thanks Dave) tell me about a railcard option for individuals that wear hearing aids that is available from National Rail. Wearing hearing aids is one of the eligibility criteria for the National Rail Disabled Persons Railcard. This railcard costs 20 pounds per year, allows travel without time of day restrictions and gives 1/3 off to the person with the railcard and one adult that is accompanying that person. If you have a registered Oyster Card, it can also be linked to it for further discounts on the tube.
This railcard can be purchased online. You do need to upload proof that you wear hearing aids. I uploaded my hearing test and receipt for the hearing aids and it was accepted. You also upload a simple picture of yourself which can be a selfie of your head similar to what one might see on a passport.
We hear a lot about the senior railcard or the two together railcard on this forum, but I don't recall hearing about this option before. That is probably because it is quite specific, but it seems to me that I know more and more people who are wearing hearing aids. Hmm, does that mean I am getting older :)