Hi Airsmiles, Hope your trip is going well.
Perhaps slightly unPC but the airlines when advised of a passenger with hearing difficulties usually put the term "DEAF" or "HOH" into the customers booking so when one checks in it will flag up next to the name.
Now the individuals dealing with you at check in will see it if they dont immediately realise when they first speak to you and should deal with you appropriately. However if you are looking for special assistance to get to the gate and off the aircraft then a wheelchair needs to be requested as BA no longer provides MAAS services (meet and assist) as it was being abused by over 90% of users as a free porter service.
However if you can make it to the gate yourself you cannot assume that the gate staff will be actively looking out for you because they have a lot to do. What I would recommend is just letting the gate staff know who you are and tell them where you will be sitting and if one of them could give you a little nod when its time to board. If you have ordered a wheelchair however this will already be done for you by the porter who brings you down. Dont worry too much about announcements as all the info you should need will be on the Information screens which I recommend you check regularly. If by the off chance you have not boarded near the end cos you lost track of time, the gate staff will be able to see from the comment next to your name and realise that you are hard of hearing. Hopefully they will send someone off to hunt for you but understandably...airports are big places and this may prove impossible.
When onboard the aircraft (especially if you are in Club) you are generally served by the same crew members. Most crew do make the effort to check the passenger list although sometimes when its hectic its just not possible to memorise the hundreds of comments that appear on it. The "DEAF" or "HOH" comment will be beside your name and if the purser is on the ball then he/she will make the effort to tell all the crew in your cabin. However do not be afraid on first contact with the crew member working your area to let him/her know, its not always easy for us to know straight away and often we need your assistance in order to assist you.
If something is wrong such as delays in the airports or something onboard and you cant make out the announcements please PLEASE do not hesitate to contact a staff/crew member, they will help you as best they can.
I hope that helps and I hope your trip was enjoyable...also hope you did plenty of crimbo shopping!
Hope to meet you on one of my flights in the future.
Best Regards!